[cntt] giáo trình sql và pl sql

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Gi¸o tr×nh SQL vµ PL/SQL

§µo t¹o c¬ b¶n: SQL vµ PL/SQL Trang 2

C«ng ty cæ phÇn ®Çu t− ph¸t triÓn c«ng nghÖ - Fpt Hµ Néi, th¸ng 11 n¨m 2002.

§µo t¹o Oracle c¬ b¶n





Môc lôc

Môc lôc .................................................................................................................................................3

1 Giíi thiÖu.......................................................................................................................................6 1.1 Môc tiªu kho¸ häc ..............................................................................................................................6 1.2 Khëi ®éng vµ tho¸t khái Oracle.........................................................................................................6

1.2.1 T¹i Server (Window NT) .........................................................................................6 1.2.2 T¹i Client (Window 9x)............................................................................................6

1.3 Giíi thiÖu ng«n ng÷ SQL ...................................................................................................................7 1.3.1 LÞch sö ph¸t triÓn cña ng«n ng÷ SQL .....................................................................7 1.3.2 ChuÈn SQL .............................................................................................................7

1.4 Çc kh¸i niÖm trong CSDL.................................................................................................................7 1.5 Danh s¸ch rót gän çc ®èi t−îng CSDL ...........................................................................................8 1.6 Çc lÖnh SQL ......................................................................................................................................8 1.7 Giíi thiÖu vÒ vÝ dô thùc hµnh.............................................................................................................9

1.7.1 M« h×nh quan hÖ d÷ liÖu..........................................................................................9 1.7.2 M« t¶ d÷ liÖu............................................................................................................9

2 LÖnh truy vÊn c¬ b¶n ...........................................................................................................10 2.1 LÖnh truy vÊn c¬ b¶n........................................................................................................................10 2.2 Çc thµnh phÇn kh¸c cña mÖnh ®Ò SELECT..................................................................................10 2.3 Gi¸ trÞ Null..........................................................................................................................................11 2.4 Läc d÷ liÖu tõ çc row cã cïng gi¸ trÞ.............................................................................................11 2.5 HiÓn thÞ cÊu tróc b¶ng ......................................................................................................................12 2.6 Çc lÖnh cña c«ng cô SQL*Plus......................................................................................................12

2.6.1 Çc lÖnh so¹n th¶o ...............................................................................................12 2.6.2 Çc lÖnh vÒ file......................................................................................................13 2.6.3 Çc lÖnh vÒ column...............................................................................................13

2.7 Bµi tËp................................................................................................................................................14

3 Truy vÊn d÷ liÖu cã ®iÒu kiÖn ............................................................................................16 3.1 MÖnh ®Ò ORDER BY .........................................................................................................................16 3.2 MÖnh ®Ò WHERE...............................................................................................................................16 3.3 Çc to¸n tö ........................................................................................................................................17 3.4 Bµi tËp................................................................................................................................................19

4 Çc hµm ¸p dông cho 1 dßng d÷ liÖu..............................................................................20 4.1 Çc hµm sè........................................................................................................................................20 4.2 Çc hµm ký tù ...................................................................................................................................22 4.3 Çc hµm ngµy ...................................................................................................................................26 4.4 Çc hµm chuyÓn ®æi kiÓu.................................................................................................................28 4.5 Bµi tËp................................................................................................................................................29

5 BiÕn runtime..............................................................................................................................31 5.1 Bµi tËp................................................................................................................................................32

6 Çc hµm nhãm ¸p dông cho lín h¬n hoÆc b»ng 1 dßng d÷ liÖu ........................32 6.1 Çc hµm t¸c ®éng trªn nhãm ..........................................................................................................32 6.2 MÖnh ®Ò GROUP BY .........................................................................................................................34 6.3 Bµi tËp................................................................................................................................................35

7 HiÓn thÞ néi dung d÷ liÖu tõ nhiÒu b¶ng........................................................................35 7.1 Mèi liªn kÕt t−¬ng ®−¬ng .................................................................................................................35




7.2 Mèi liªn kÕt kh«ng t−¬ng ®−¬ng......................................................................................................35 7.3 Mèi liªn kÕt céng...............................................................................................................................36 7.4 Liªn kÕt cña b¶ng víi chÝnh nã .......................................................................................................36 7.5 Çc to¸n tö tËp hîp ..........................................................................................................................36 7.6 Bµi tËp................................................................................................................................................37

8 Çc lÖnh truy vÊn lång nhau...........................................................................................39 8.1 C©u lÖnh SELECT lång nhau. ..........................................................................................................39 8.2 Bµi tËp................................................................................................................................................40

9 CÊu tróc h×nh c©y...................................................................................................................40 9.1 CÊu tróc h×nh c©y trong 1 table .......................................................................................................40 9.2 Kü thuËt thùc hiÖn ............................................................................................................................41 9.3 Bµi tËp................................................................................................................................................42

10 Tæng kÕt vÒ lÖnh select .....................................................................................................44

11 T¹o table ...................................................................................................................................44 11.1 LÖnh t¹o b¶ng ...................................................................................................................................44 11.2 Çc quy t¾c ®Æt tªn object ...............................................................................................................46 11.3 Çc quy t¾c khi tham chiÕu ®Õn object...........................................................................................47 11.4 KiÓu d÷ liÖu vµ ®iÒu kiÖn..................................................................................................................47

11.4.1 CHAR ....................................................................................................................47 11.4.2 VARCHAR2...........................................................................................................48 11.4.3 VARCHAR.............................................................................................................48 11.4.4 NUMBER...............................................................................................................48 11.4.5 FLOAT...................................................................................................................48 11.4.6 LONG ....................................................................................................................49 11.4.7 DATE.....................................................................................................................49 11.4.8 RAW vµ LONG RAW ............................................................................................50 11.4.9 ROWID..................................................................................................................50 11.4.10 MLSLABEL............................................................................................................50 11.4.11 ChuyÓn ®æi kiÓu ....................................................................................................50

11.5 Constraint..........................................................................................................................................51 11.6 Bµi tËp................................................................................................................................................52

12 çc lÖnh DDL kh¸c vµ d÷ liÖu trong tõ ®iÓn d÷ liÖu...............................................52 12.1 ChØnh söa cÊu tróc table ..................................................................................................................52 12.2 Çc lÖnh DDL kh¸c ...........................................................................................................................53

12.2.1 Xãa table ...............................................................................................................53 12.2.2 Gi¶i thÝch b¶ng ......................................................................................................53 12.2.3 Thay ®æi tªn object................................................................................................53 12.2.4 Xãa d÷ liÖu cña table.............................................................................................53

12.3 D÷ liÖu trong tõ ®iÓn d÷ liÖu ............................................................................................................54 12.4 Bµi tËp................................................................................................................................................54

13 Çc lÖnh Thao t¸c d÷ liÖu kh¸c ......................................................................................55 13.1 ChÌn mét row vµo table ...................................................................................................................55 13.2 ChØnh söa d÷ liÖu..............................................................................................................................55 13.3 Xãa dßng ...........................................................................................................................................55 13.4 Lçi rµng buéc d÷ liÖu .......................................................................................................................56 13.5 LÖnh ®iÒu khiÓn giao dÞch................................................................................................................56 13.6 Bµi tËp................................................................................................................................................57

14 Sequence vµ index..................................................................................................................57




14.1 Sequence...........................................................................................................................................57 14.1.1 T¹o Sequence.......................................................................................................57 14.1.2 Xo¸ vµ söa sequence ...........................................................................................58

14.2 Index ..................................................................................................................................................58 14.3 Bµi tËp................................................................................................................................................59

15 T¹o view ......................................................................................................................................59 15.1 View....................................................................................................................................................59 15.2 Bµi tËp................................................................................................................................................61

16 QuyÒn vµ b¶o mËt ...................................................................................................................61 16.1 QuyÒn - PRIVILEGE ..........................................................................................................................61 16.2 ROLE..................................................................................................................................................62 16.3 Synonym............................................................................................................................................63

17 tæng quan vÒ pl/sql vµ procedure builder...............................................................63 17.1 Có ph¸p lÖnh PL/SQL .......................................................................................................................63 17.2 PL/SQL block ....................................................................................................................................63 17.3 Giíi thiÖu Procedure builder............................................................................................................64

18 có ph¸p lËp tr×nh ...................................................................................................................66 18.1 IF ........................................................................................................................................................66 18.2 LOOP vµ EXIT....................................................................................................................................66 18.3 FOR ....................................................................................................................................................67 18.4 WHILE ................................................................................................................................................67 18.5 GOTO .................................................................................................................................................67

19 cursor ........................................................................................................................................68 19.1 §Þnh nghÜa .........................................................................................................................................68 19.2 KiÓu d÷ liÖu Table vµ Record...........................................................................................................69 19.3 Sao kiÓu d÷ liÖu ................................................................................................................................70 19.4 C©u lÖnh SELECT... INTO... trong PL/SQL......................................................................................70 19.5 Bµi tËp................................................................................................................................................70

20 procedure vµ funtion..........................................................................................................71 20.1 Procedure ..........................................................................................................................................71 20.2 Function.............................................................................................................................................72 20.3 Bµi tËp................................................................................................................................................73

21 pakage.........................................................................................................................................73 21.1 Package .............................................................................................................................................73

22 database trigger ..................................................................................................................74 22.1 Database Trigger...............................................................................................................................74 22.2 Bµi tËp................................................................................................................................................75

23 error handing.........................................................................................................................76 23.1 Bµi tËp................................................................................................................................................78




1 Giíi thiÖu

1.1 Môc tiªu kho¸ häc

KÕt thóc kho¸ häc häc viªn ph¶i n¾m ®−îc

• HiÓu ®−îc ph−¬ng ph¸p, çc thµnh phÇn, thuËt ng÷ vµ thao t¸c trong CSDL quan hÖ

• T¹o ®−îc çc cÊu tróc d÷ liÖu nh− table, view dïng SQL

• Ghi, ®äc, vµ cËp nhËt d÷ liÖu trong CSDL

• X©y dùng çc PL/SQL block dïng Procedure Builder

1.2 Khëi ®éng vµ tho¸t khái Oracle

1.2.1 T¹i Server (Window NT)

SQLDBA cung cÊp çc dÞch vô qu¶n trÞ hÖ thèng, nh−: t¹o lËp CSDL, më - ®ãng CSDL, t¹o vµ qu¶n lý çc USER ... Çc b−íc ®Ó khëi ®éng t¹i Server nh− sau:

• Khëi ®éng m¸y chñ

• BËt dÞch vô OracleServiceXXX (trong ®ã XXX lµ tªn cña CSDL) b»ng çch nhÊn vµo Start -> Program -> Service -> OracleServiceXXX -> NhÊn chuét ph¶i -> NhÊn Start. Chó ý chØ bËt dÞch vô nµy khi ng−êi cµi ®Æt kh«ng ®Ó chÕ ®é tù ®éng hay khi dÞch vô nµy ch−a ®−îc bËt.

• BËt dÞch vô OracleXXXTNSLÝstener (trong ®ã XXX lµ tªn cña Database Home) b»ng çch nhÊn vµo Start -> Program -> Service -> OracleXXXTNSLÝstener -> NhÊn chuét ph¶i -> NhÊn Start. Chó ý chØ bËt dÞch vô nµy khi ng−êi cµi ®Æt kh«ng ®Ó chÕ ®é tù ®éng hay khi dÞch vô nµy ch−a ®−îc bËt.

• Khi bËt xong CSDL ®· s½n sµng ®Ó lµm viÖc

§Ó ®ãng CSDL cÇn lµm theo çc b−íc ng−îc l¹i:

• T¾t dÞch vô OracleXXXTNSLÝstener (trong ®ã XXX lµ tªn cña Database Home) b»ng çch nhÊn vµo Start -> Program -> Service -> OracleXXXTNSLÝstener -> NhÊn chuét ph¶i -> NhÊn Stop.

• T¾t dÞch vô OracleServiceXXX (trong ®ã XXX lµ tªn cña CSDL) b»ng çch nhÊn vµo Start -> Program -> Service -> OracleServiceXXX -> NhÊn chuét ph¶i -> NhÊn Stop.

• Shutdown m¸y chñ.

1.2.2 T¹i Client (Window 9x)

Çc øng dông cña oracle ch¹y trong m«i tr−êng Windows víi giao diÖn graphic, çc øng dông th−êng dïng cã SQL*Plus, Oracle Form, Oracle Report, Oracle Designer ... ViÖc ch¹y çc øng dông nµy hoµn toµn gièng nh− viÖc ch¹y çc øng dông th«ng th−êng trong m«i tr−êng windows.

§Ó lµm viÖc víi çc øng dông truy cËp CSDL Oracle, ng−êi sö dông (NSD) ph¶i connect vµo CSDL. Cã hai çch ®Ó connect.

Connect NSD/password, vÝ dô NSD tªn Scott cã password lµ tiger th×

Connect Scott/tiger

Ph¸t lÖnh connect víi tªn NSD, khi ®ã Oracle sÏ hái password

Connect Scott

Enter password: *****




NSD cã thÓ lµm viÖc trong ph¹m vi cho phÐp cña m×nh mµ Oracle gäi lµ "khung c¶nh" (Schema) cña NSD. Mçi khung c¶nh chøa nhiÒu ®èi t−îng çc lo¹i, NSD chØ cã thÓ t¸c ®éng lªn çc ®èi t−îng trong khung c¶nh cña m×nh.

Trong çc øng dông ®Òu cã chøc n¨ng tho¸t vµ tù ®éng disconnect.

§Ó thùc hµnh phÇn SQL vµ PL/SQL gäi øng dông SQL* Plus.

1.3 Giíi thiÖu ng«n ng÷ SQL

1.3.1 LÞch sö ph¸t triÓn cña ng«n ng÷ SQL

M« h×nh c¬ së d÷ liÖu (CSDL) quan hÖ do E.F Codd ®−a ra vµo ®Çu thËp kû 70, tõ ®ã ®Õn nay nã liªn tôc ph¸t triÓn trë thµnh m« h×nh CSDL phæ biÕn bËc nhÊt (RDBMS). M« h×nh quan hÖ gåm çc thµnh phÇn sau:

• TËp hîp çc ®èi t−îng vµ/hoÆc çc mèi quan hÖ

• TËp hîp çc xö lý t¸c ®éng tíi çc quan hÖ

• Rµng buéc d÷ liÖu ®¶m b¶o tÝnh chÝnh x¸c vµ nhÊt qu¸n.

SQL (Structured Query Language, ®äc lµ "sequel") lµ tËp lÖnh truy xuÊt CSDL quan hÖ. Ng«n ng÷ SQL ®−îc IBM sö dông ®Çu tiªn trong hÖ qu¶n trÞ CSDL System R vµo gi÷a nh÷ng n¨m 70, hÖ ng«n ng÷ SQL ®Çu tiªn (SEQUEL2) ®−îc IBM c«ng bè vµo th¸ng 11 n¨m 1976. N¨m 1979, tËp ®oµn ORACLE giíi thiÖu th−¬ng phÈm ®Çu tiªn cña SQL, SQL còng ®−îc cµi ®Æt trong çc hÖ qu¶n trÞ CSDL nh− DB2 cña IBM vµ SQL/DS.

Ngµy nay, SQL ®−îc sö dông réng r·i vµ ®uîc xem lµ ng«n ng÷ chuÈn ®Ó truy cËp CSDL quan hÖ.

1.3.2 ChuÈn SQL

N¨m 1989, viÖn tiªu chuÈn quèc gia Hoa kú (ANSI) c«ng nhËn SQL lµ ng«n ng÷ chuÈn ®Ó truy cËp CSDL quan hÖ trong v¨n b¶n ANSI SQL89.

N¨m 1989, tæ chøc tiªu chuÈn quèc tÕ (ISO) c«ng nhËn SQL ng«n ng÷ chuÈn ®Ó truy cËp CSDL quan hÖ trong v¨n b¶n ISO 9075-1989.

TÊt c¶ çc hÖ qu¶n trÞ CSDL lín trªn thÕ giíi cho phÐp truy cËp b»ng SQL vµ hÇu hÕt theo chuÈn ANSI.

1.4 Çc kh¸i niÖm trong CSDL

Table lµ cÊu tróc l−u tr÷ c¬ b¶n nhÊt trong CSDL quan hÖ (RDBMS), nã bao gåm 1 hoÆc nhiÒu column vµ 0 hoÆc nhiÒu row.

Row lµ tæ hîp nh÷ng gi¸ trÞ cña Column trong b¶ng. Mét row cßn cã thÓ ®−îc gäi lµ 1 record.

Column hiÓn thÞ mét lo¹i d÷ liÖu trong b¶ng, vÝ dô tªn phßng ban trong b¶ng phßng ban. Ng−êi ta thÓ hiÖn nã th«ng qua tªn column vµ gi÷ sè liÖu d−íi çc kiÓu vµ kÝch cì nhÊt ®Þnh.

Field lµ giao cña column vµ row. Field chÝnh lµ n¬i chøa d÷ liÖu. NÕu kh«ng cã d÷ liÖu trong field ng−êi ta nãi field cã gia trÞ lµ null.

Primary Key lµ mét column hoÆc mét tËp çc column x¸c ®Þnh tÝnh duy nhÊt cña çc row ë trong b¶ng. VÝ dô m· phßng ban. Primary Key nhÊt thiÕt ph¶i cã sè liÖu.

Foreign Key lµ mét column hoÆc mét tËp çc column tham chiÕu tíi chÝnh b¶ng ®ã hoÆc mét b¶ng kh¸c. Foreign Key x¸c ®Þnh mèi quan hÖ gi÷a çc b¶ng.

Constraint lµ çc rµng buéc d÷ liÖu, vÝ dô Foreign Key, Primary Key...




VÝ dô:

10 CLARK 7782

30 BLAKE 7698

30 MARTIN 7654

20 JONES 7566

30 WARD 7521

30 ALLEN 7499

20 SMITH 7369

DEPTNODEPTEMP

ENAME EMPNO

OPERATIONS 40

SALES 30

RESEARCH 20

ACCOUNTING 10

DNAME DEPTNO

DEPT EMP

Primary key

Foreign key

Column

Row

1.5 Danh s¸ch rót gän çc ®èi t−îng CSDL

Table lµ cÊu tróc l−u tr÷ c¬ b¶n nhÊt trong CSDL quan hÖ (RDBMS), gåm row vµ column

View lµ cÊu tróc logic hiÓn thÞ d÷ liÖu tõ 1 hoÆc nhiÒu b¶ng

Sequence kÕt sinh gi¸ trÞ cho çc primary key

Index t¨ng tÝnh thùc thi cña çu truy vÊn

Synonym tªn t−¬ng ®−¬ng cña ®èi t−îng

Program unit gåm Procedure, function, package...

1.6 Çc lÖnh SQL

LÖnh M« t¶

SELECT Lµ lÖnh th«ng dông nhÊt, dïng ®Ó lÊy, xem d÷ liÖu trong CSDL.

INSERT UPDATE DELETE

Lµ 3 lÖnh dïng ®Ó nhËp thªm nh÷ng row míi, thay ®æi néi dung d÷ liÖu trªn çc row hay xo¸ çc row trong table. Nh÷ng lÖnh nµy ®−îc gäi lµ çc lÖnh thao t¸c d÷ liÖu DML (Data Manipulation Language)

CREATE ALTER DROP RENAME TRUNCATE

Lµ 3 lÖnh dïng ®Ó thiÕt lËp, thay ®æi hay xo¸ bá cÊu tróc d÷ liÖu nh− lµ table, view, index. Nh÷ng lÖnh nµy ®−îc gäi lµ çc lÖnh ®Þnh nghÜa d÷ liÖu DDL (Data Definition Language)

COMMIT ROLLBACK SAVE POINT

Qu¶n lý viÖc thay ®æi d÷ liÖu b»ng çc lÖnh DML. ViÖc thay ®æi d÷ liÖu cã thÓ ®−îc nhãm l¹i thµnh çc transaction.

GRANT REVOKE 2 lÖnh nµy dïng ®Ó g¸n hoÆc huû çc quyÒn truy nhËp vµo CSDL Oracle vµ çc cÊu

tróc bªn trong nã. Nh÷ng lÖnh nµy ®−îc gäi lµ çc lÖnh ®iÒu khiÓn d÷ liÖu DCL (Data




Control Language)

1.7 Giíi thiÖu vÒ vÝ dô thùc hµnh

1.7.1 M« h×nh quan hÖ d÷ liÖu

EMP

DEPT

BONUS

SALGRADE

DUMMY

1.7.2 M« t¶ d÷ liÖu

Tªn KiÓu Kho¸ Gi¶i thÝch

DEPT DEPTNO NUMBER(2) NOT NULL PK M· phßng ban DNAME CHAR(14) Tªn phßng ban LOC CHAR(13) §Þa chØ

SALGRADE GRADE NUMBER PK Møc l¬ng LOSAL NUMBER Gi¸ trÞ thÊp HISAL NUMBER Gi¸ trÞ cao

EMP EMPNO NUMBER(4) NOT NULL, PK M· nh©n viªn ENAME CHAR(10), Tªn nh©n viªn JOB CHAR(9), NghÒ nghiÖp MGR NUMBER(4) FK (EMP.EMPNO) M· ng−êi qu¶n lý HIREDATE DATE Ngµy gia nhËp c«ng ty SAL NUMBER(7,2) L−¬ng COMM NUMBER(7,2) Th−ëng DEPTNO NUMBER(2) NOT NULL, FK (DEPT.DEPTNO) M· phßng ban




2 LÖnh truy vÊn c¬ b¶n

2.1 LÖnh truy vÊn c¬ b¶n

SELECT [DISTINCT ] {*, column [alias],...} FROM table;

• SELECT tr¶ lêi c©u hái lÊy d÷ liÖu nµo? (column, biÓu thøc...), trong mÖnh ®Ò SELECT cÇn cã Ýt nhÊt 1 column.

• FROM tr¶ lêi c©u hái lÊy d÷ liÖu ë ®Çu? (table, view...)

• DISTINCT chØ ®Þnh hiÓn thÞ 1 lÇn çc d÷ liÖu trïng nhau.

• * thay cho viÖc chØ tªn tÊt c¶ çc column

• alias ®−a ra nh·n cña column hiÓn thÞ d÷ liÖu.

Vd:

SELECT * FROM emp; SELECT empno, ename, deptno, mgr FROM emp; SELECT DISTINCT job nghenghiep FROM emp;

2.2 Çc thµnh phÇn kh¸c cña mÖnh ®Ò SELECT

Trong mÖnh ®Ò SELECT cßn cã thÓ ®−a vµo çc thµnh phÇn kh¸c:

• BiÓu thøc to¸n häc

• Column alias

• Çc column ®−îc ghÐp chuçi

• Literal

BiÓu thøc to¸n häc

Trong mÖnh ®Ò SELECT biÓu thøc to¸n häc cã thÓ çc gi¸ trÞ (column hoÆc hµng sè), çc to¸n tö, çc hµm. Çc to¸n tö ®−îc dïng lµ (+), (-), (*), (/). §é −u tiªn cña çc to¸n tö gièng trong phÇn sè häc. Vd:

SELECT ename, sal *12, comm FROM emp; SELECT ename, (sal+250)*12 FROM emp;

Column alias

Trong mÖnh ®Ò SELECT, column alias lµ phÇn nh·n hiÓn thÞ cña column khi lÊy sè liÖu ra. Trong column alias kh«ng ®−îc cã dÊu çch vµ viÕt çch sau tªn column mét dÊu çch. Column alias ®−îc chÊp nhËn cã dÊu çch khi ®−îc ®Æt trong dÊu nh¸y kÐp (“ “).

Vd: (ANUAL chÝnh lµ column alias)

SELECT ename, SAL*12 ANUAL, comm FROM emp;

Çc column ®−îc ghÐp chuçi

To¸n tö ghÐp chuçi (||) cho phÐp çc column ®−îc nèi víi nhau thµnh d¹ng chuçi. Cã thÓ cã nhiÒu to¸n tö ghÐp chuçi trong cïng mét column alias. Vd:

SELECT empno||ename EMPLOYEE FROM emp; SELECT ename || ' co luong la ' || (sal+250)*12 as "mieu ta" FROM emp;

Chuçi ®Æt trong nh¸y ®¬n, bÝ danh ®Æt trong nh¸y kÐp




Literal

Trong mÖnh ®Ò SELECT, literal lµ bÊt kú ký tù nµo, biÓu thøc, hay sè nµp mµ kh«ng ph¶i lµ column hoÆc column alias. Vd:

SELECT empno||ename EMPLOYEE, ‘WORK IN DEPARTMENT’, deptno FROM emp;

2.3 Gi¸ trÞ Null

Cét cã gi¸ trÞ rçng (NULL) lµ cét ch−a ®−îc g¸n gi¸ trÞ, nãi çch kh¸c nã ch−a ®−îc khëi t¹o gi¸ trÞ. Çc cét víi bÊt cø kiÓu d÷ liÖu nµo còng cã thÓ cã trÞ NULL, trõ khi ®−îc nã lµ khãa hay cã rµng buéc toµn vÑn NOT NULL. Trong biÓu thøc cã bÊt kú gi¸ trÞ NULL nµo kÕt qu¶ còng lµ NULL. Vd:

SELECT ename, sal*12 + comm ANUAL_SAL FROM emp;

NULL trong çc hµm cña SQL

- Trong çc hµm lµm viÖc víi tõng cét hay hµm v« h−íng (scalar function)

Çc hµm lo¹i nµy tr¶ vÒ trÞ null khi cã tham sè null, trõ hµm NVL vµ TRANSLATE cã thÓ tr¶ vÒ gi¸ trÞ thùc.

Có ph¸p cña hµm NVL

NVL (DATECOLUMN,’01-01-2001’) NVL(NUMBERCOLUMN, 9) NVL(CHARCOLUMN,’STRING’)

VÝ dô: NVL(comm,0) tr¶ vÒ trÞ 0 khi comm lµ null

SELECT ename, sal*12 + NVL(comm,0) ANUAL_SAL FROM emp;

- Trong çc hµm lµm viÖc víi nhãm çc cét (group function)

HÇu hÕt çc hµm lµm viÖc trªn nhãm bá qua trÞ null, vÝ dô nh− khi sö dông hµm AVG ®Ó tÝnh trung b×nh cho mét cét cã çc gi¸ trÞ 1000, null, null, null, 2000 khi ®ã trung b×nh ®−îc tÝnh lµ (1000+2000)/2=1500, nh− vËy trÞ null bÞ bá qua chø kh«ng ph¶i xem lµ trÞ 0.

NULL trong çc biÓu thøc so s¸nh, ®iÒu kiÖn

§Ó kiÓm tra cã ph¶i null hay kh«ng dïng çc to¸n tö IS NULL hoÆc IS NOT NULL. NÕu trong biÓu thøc so s¸nh cã trÞ null tham gia vµ kÕt qu¶ cña biÓu thøc phô thuéc vµo trÞ null th× kÕt qu¶ lµ kh«ng x¸c ®Þnh, tuy nhiªn trong biÓu thøc DECODE, hai gi¸ trÞ null ®−îc xem lµ b»ng nhau trong phÐp so s¸nh.

ORACLE xem çc biÓu thøc víi kÕt qu¶ kh«ng x¸c ®Þnh t−¬ng ®−¬ng víi FALSE, vÝ dô comm = NULL cã kÕt qu¶ kh«ng x¸c ®Þnh vµ do ®ã biÓu thøc so s¸nh xem nh− cho kÕt qu¶ FALSE. Trong c©u lÖnh sau kh«ng cã mÉu tin nµo ®−îc chän

SELECT * FROM emp WHERE comm=NULL;

NÕu muèn chän çc nh©n viªn cã comm lµ NULL th× ph¶i dïng to¸n tö IS NULL

SELECT * FROM emp WHERE comm IS NULL;

2.4 Läc d÷ liÖu tõ çc row cã cïng gi¸ trÞ

Mét c©u lÖnh truy vÊn cã thÓ tr¶ vÒ çc row cã cïng gÝa trÞ. Vd:

SELECT JOB FROM EMP; SELECT DEPTNO FROM EMP; SELECT JOB, DEPTNO FROM EMP;




§Ó läc lÊy mét gi¸ trÞ duy nhÊt ng−êi ta dïng mÖnh ®Ò DISTINCT. MÖnh ®Ò nµy ph¶i ®−îc ®Æt tr−íc tÊt c¶ çc column, sau mÖnh ®Ò SELECT. Vd:

SELECT DISTINCT JOB FROM EMP; SELECT DISTINCT DEPTNO FROM EMP; SELECT DISTINCT JOB, DEPTNO FROM EMP;

2.5 HiÓn thÞ cÊu tróc b¶ng

Có ph¸p

DESC[RIBE] table_name

(lÖnh nµy chØ ch¹y ®−îc trªn sqlplus, kh«ng ch¹y ®−îc trªn PL/SQL Develop)

VÝ dô:

DESC emp; Name Null? Type ------------------------------- -------- ---- EMPNO NOT NULL NUMBER(4) ENAME VARCHAR2(10) JOB VARCHAR2(9) MGR NUMBER(4) HIREDATE DATE SAL NUMBER(7,2) COMM NUMBER(7,2) DEPTNO NUMBER(2)

KiÓu d÷ liÖu NOT NULL nghÜa lµ column nhÊt ®Þnh ph¶i cã gi¸ trÞ.

2.6 Çc lÖnh cña c«ng cô SQL*Plus

2.6.1 Çc lÖnh so¹n th¶o

LÖnh M« t¶

A[PPEND] text §−a thªm ®o¹n text vµo dßng hiÖn t¹i

C[HANGE] /old/new ChuyÓn ®o¹n text cò thµnh ®o¹n text míi trong dßng hiÖn t¹i

C[HANGE] /text/ Xo¸ ®o¹n text trong dßng hiÖn t¹i

CL[EAR] BUFF[ER] Xo¸ tÊt c¶ çc dßng trong SQL buffer

DEL Xo¸ dßng hiÖn t¹i

DEL n Xo¸ dßng n

DEL m n Xo¸ dßng tõ m ®Õn n

I[NPUT] Thªm mét sè dßng nhÊt ®Þnh

I[NPUT] text Thªm dßng cã chøa text

L[IST] LiÖt kª toµn bé çc dßng trong SQL buffer

L[IST] n LiÖt kª dßng n

L[IST] m n LiÖt kª dßng m ®Õn n




R[UN] HiÓn thÞ vµ ch¹y lÖnh trong buffer

N Nhµy ®Õn dßng n

N text Thay dßng n bëi ®o¹n text

0 text ChÌn 1 dßng tr−íc dßng 1

2.6.2 Çc lÖnh vÒ file

LÖnh M« t¶

SAVE filename [.ext] [REP[LACE]|APP[END]] Ghi néi dung bufer thµnh file. APPEND ®Ó ghi thªm vµo file. REPLACE ®Ó chÌn lªn néi dung file cò.

GET filename [.ext] Ghi néi dung file vµo buffer. MÆc ®Þnh phÇn ®u«i lµ .sql

STA[RT] filename [.ext] Ch¹y çc lÖnh trong file

@ filename [.ext] Gièng lÖnh Start

ED[IT] So¹n th¶o néi dung bufffer cã tªn lµ afiedt.buf

§Ó ch¹y néi dung buffer dïng lÖnh /

ED[IT] filename [.ext ] So¹n th¶o néi dung file

SPO[OL] filename [.ext ] [OFF|OUT] CÊt kÕt qu¶ hiÓn thÞ trªn mµn h×nh ra file. Vd:

SPOOL result.sql .... SPOOL OFF

EXIT Tho¸t khái SQL*Plus

2.6.3 Çc lÖnh vÒ column

Có ph¸p

COLUMN [{column | alias} [option]]

LÖnh M« t¶

CLE[AR] Xo¸ ®Þnh d¹ng cña column

FOR[MAT] format ChuyÓn ®Þnh d¹ng cña cét d÷ liÖu

HEA[DING] text §Æt nh·n co column

JUS[TIFY] align Çn tr¸i “ left , ph¶i - right, gi÷a - center cho nh·n

NOPRI[NT]

Èn column

NUL[L] text HiÓn thÞ text nÕu gi¸ trÞ cña column lµ NULL

PRI[NT} HiÓn thÞ column




TRU[NCATED] Xo¸ chuçi t¹i cuèi dßng ®Çu tiªn khi hiÓn thÞ

WRA[PPED] Phñ cuèi chuçi cña dßng tiÕp theo

WOR[D_WAPPED] Gièng WAP nh−ng tõ kh«ng bÞ c¾t

L−u ý: çc ®Þnh d¹ng hiÓn thÞ nµy ®−îc l−u vµo bé nhí vµ ¸p dông cho mäi cét cã tªn nh− vËy, dï chóng ë trong b¶ng nµo

Vd: ChØnh ®Þnh d¹ng vµ nh·n cña column

COLUMN ename HEADING ‘Employee|Name’ FORMAT A15 COLUMN sal JUSTIFY LEFT FORMAT $ 99,990.00 COLUMN hiredate FORMAT A9 NULL ‘ Not hired’

Vd: HiÓn thÞ ®Þnh d¹ng hiÖn t¹i cña column

COLUMN COLUMN ename

Vd: Xo¸ ®Þnh d¹ng hiÖn t¹i cña column

COLUMN ename CLEAR CLEAR COLUMN

Çc lo¹i ®Þnh d¹ng

§Þnh d¹ng

M« t¶ VÝ dô KÕt qu¶

An HiÓn thÞ dµi nhÊt n ký tù dïng cho çc column d¹ng ký tù hoÆc d¹ng ngµy

9 HiÓn thÞ sè, kh«ng bao gåm sè 0 999999 1234

0 HiÓn thÞ c¶ sè 0 099999 01234

$ HiÓn thi $ $9999 $1234

L HiÓn thÞ ký tù L L9999 L1234

. HiÓn thÞ dÊu thËp ph©n 9999.99 1234.00

, HiÓn thÞ dÊu ph©n chia hµng ngh×n 9,999 1,234

2.7 Bµi tËp

1. Chän toµn bé th«ng tin trong b¶ng SALGRADE

GRADE LOSAL HISAL ---------- ---------- ---------- 1 700 1200 2 1201 1400 3 1401 2000 4 2001 3000 5 3001 9999

2. Chän toµn bé th«ng tin trong b¶ng EMP

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ------ ---------- --------- ----- --------- ----- ------ ---------- 7839 KING PRESIDENT 17-11-1981 5000 10 7698 BLAKE MANAGER 7839 01-05-1981 2850 30 7782 CLARK MANAGER 7839 09-06-1981 2450 10 7566 JONES MANAGER 7839 02-04-1981 2975 20




7654 MARTIN SALESMAN 7698 28-09-1981 1250 1400 30 7499 ALLEN SALESMAN 7698 20-02-1981 1600 300 30 7844 TURNER SALESMAN 7698 08-09-1981 1500 0 30 7900 JAMES CLERK 7698 03-12-1981 950 30 7521 WARD SALESMAN 7698 22-02-1981 1250 500 30 7902 FORD ANALYST 7566 03-12-1981 3000 20 7369 SMITH CLERK 7902 17-12-1980 800 20 7788 SCOTT ANALYST 7566 09-12-1982 3000 20 7876 ADAMS CLERK 7788 12-01-1983 1100 20 7934 MILLER CLERK 7782 23-01-1982 1300 10

3. HiÓn thÞ mäi lo¹i nghÒ nghiÖp

JOB --------- ANALYST CLERK MANAGER PRESIDENT SALESMAN

4. HiÓn thÞ tªn nh©n viªn vµ thu nhËp trong mét n¨m (REMUNERATION)

ENAME REMUNERATION ---------- ------------ KING 60000 BLAKE 34200 CLARK 29400 JONES 35700 MARTIN 16400 ALLEN 19500 TURNER 18000 JAMES 11400 WARD 15500 FORD 36000 SMITH 9600 SCOTT 36000 ADAMS 13200 MILLER 15600 14 rows selected.

5. HiÓn thÞ theo néi dung d−íi ®©y

Who, what and when ---------------------------------------------------------------------- KING HAS HELP THE POSITION OF PRESIDENT IN DEPT 10 SINCE 17-11-1981 BLAKE HAS HELP THE POSITION OF MANAGER IN DEPT 30 SINCE 01-05-1981 CLARK HAS HELP THE POSITION OF MANAGER IN DEPT 10 SINCE 09-06-1981 JONES HAS HELP THE POSITION OF MANAGER IN DEPT 20 SINCE 02-04-1981 MARTIN HAS HELP THE POSITION OF SALESMAN IN DEPT 30 SINCE 28-09-1981 ALLEN HAS HELP THE POSITION OF SALESMAN IN DEPT 30 SINCE 20-02-1981 TURNER HAS HELP THE POSITION OF SALESMAN IN DEPT 30 SINCE 08-09-1981 JAMES HAS HELP THE POSITION OF CLERK IN DEPT 30 SINCE 03-12-1981 WARD HAS HELP THE POSITION OF SALESMAN IN DEPT 30 SINCE 22-02-1981 FORD HAS HELP THE POSITION OF ANALYST IN DEPT 20 SINCE 03-12-1981 SMITH HAS HELP THE POSITION OF CLERK IN DEPT 20 SINCE 17-12-1980 SCOTT HAS HELP THE POSITION OF ANALYST IN DEPT 20 SINCE 09-12-1982 ADAMS HAS HELP THE POSITION OF CLERK IN DEPT 20 SINCE 12-01-1983 MILLER HAS HELP THE POSITION OF CLERK IN DEPT 10 SINCE 23-01-1982 14 rows selected.

6. HiÓn thÞ cÊu tróc b¶ng emp;

7. Thay ®æi nh·n vµ ®Þnh d¹ng hiÓn thÞ cña cét sal vµ hiredate trong b¶ng emp;




3 Truy vÊn d÷ liÖu cã ®iÒu kiÖn

3.1 MÖnh ®Ò ORDER BY

Có ph¸p

SELECT [DISTINCT ] {*, column [alias],...} FROM table; [WHERE condition] [ORDER BY expr/position [DESC/ASC]]

MÖnh ®Ò ORDER BY dïng ®Ó s¾p xÕp sè liÖu ®−îc hiÓn thÞ vµ ph¶i ®Æt ë vÞ trÝ sau cïng cña c©u lÖnh truy vÊn, VÝ dô:

SELECT ENAME, JOB, SAL*12, DEPTNO FROM EMP ORDER BY ENAME;

MÖnh ®Ó ORDER BY mÆc ®Þnh s¾p xÕp theo thø tù t¨ng dÇn ASC[ENDING]

• Sè thÊp tr−íc

• Ngµy nhá tr−íc

• Ký tù theo b¶ng ch÷ çi

§Ó s¾p xÕp theo thø tù ng−îc l¹i (gi¶m dÇn) ®Æt tõ kho¸ DESC[ENDING] sau column cÇn s¾p thø tù. Vi dô:

SELECT ENAME, JOB, HIREDATE FROM EMP ORDER BY HIREDATE DESC ;

Order nhiÒu column

MÖnh ®Ò Order cßn cã thÓ s¾p xÕp nhiÒu column. Çc column cÇn s¾p xÕp ®−îc viÕt thø tù sau mÖnh ®Ò ORDER BY vµ çch bëi dÊu phÈy (,). Column nµo gÇn mÖnh ®Ó ORDER BY h¬n cã møc ®é −u tiªn khi s¾p xÕp cao h¬n. ChØ ®Þnh çch thøc s¾p xÕp ASC/DESC ®−îc viÕt sau column çch bëi mét dÊu çch. VÝ dô:

SELECT DEPTNO, JOB, ENAME, SAL FROM EMP ORDER BY DEPTNO, SAL DESC ;

Order gi¸ trÞ NULL

Riªng ®èi víi gi¸ trÞ NULL, nÕu s¾p xÕp theo thø tù ASCENDING sÏ n»m ë çc vÞ trÝ cuèi cïng.

Chó ý

Cã thÓ chØ ®Þnh s¾p xÕp theo thø tù çc column trong mÖnh ®Ò SELECT. VÝ dô:

SELECT DEPTNO, JOB, ENAME, SAL FROM EMP

ORDER BY 2;

3.2 MÖnh ®Ò WHERE

Có ph¸p

SELECT [DISTINCT ] {*, column [alias],...} FROM table; [WHERE condition (s)] [ORDER BY expr/position [DESC/ASC]]




MÖnh ®Ò WHERE dïng ®Ó ®Æt ®iÒu kiÖn cho toµn bé c©u lÖnh truy vÊn. Trong mÖnh ®Ò WHERE cã thÓ cã çc thµnh phÇn:

• Tªn column

• To¸n tö so s¸nh

• Tªn column, h»ng sè hoÆc danh s¸ch çc gi¸ trÞ

VÝ dô:

SELECT DEPTNO, JOB, ENAME, SAL FROM EMP WHERE SAL BETWEEN 1000 AND 2000 ;

Truy vÊn d÷ liÖu víi nhiÒu ®iÒu kiÖn

MÖnh ®Ò WHERE cho phÐp ghÐp ®−îc nhiÒu ®iÒu kiÖn th«ng qua çc to¸n tö logic AND/OR. To¸n tö AND yªu cÇu d÷ liÖu ph¶i tho¶ m·n c¶ 2 ®iÒu kiÖn. To¸n tö OR cho phÐp d÷ liÖu tho¶ m·n 1 trong 2 ®iÒu kiÖn. VÝ dô:

SELECT DEPTNO, JOB, ENAME, SAL FROM EMP WHERE SAL BETWEEN 1000 AND 2000 AND JOB = ‘MANAGER’; SELECT DEPTNO, JOB, ENAME, SAL FROM EMP WHERE SAL BETWEEN 1000 AND 2000 OR JOB = ‘MANAGER’; SELECT DEPTNO, JOB, EMPNO, ENAME, SAL FROM EMP WHERE SAL > 1500 AND JOB = ‘MANAGER’ OR JOB =’SALESMAN’; SELECT DEPTNO, JOB, EMPNO, ENAME, SAL FROM EMP WHERE SAL > 1500 AND (JOB = ‘MANAGER’ OR JOB =’SALESMAN’);

3.3 Çc to¸n tö

To¸n tö so s¸nh

• = : To¸n tö b»ng hay t−¬ng ®−¬ng

• !=, ^=, '+, <\> : To¸n tö kh¸c hay kh«ng t−¬ng ®−¬ng

• > : To¸n tö lín h¬n

• < : To¸n tö nhá h¬n

• >= : To¸n tö lín h¬n hoÆc b»ng

• <= : To¸n tö nhá h¬n hoÆc b»ng

Çc to¸n tö logic

• NOT : Phñ ®Þnh mÖnh ®Ò

• AND : yªu cÇu d÷ liÖu ph¶i tho¶ m·n c¶ 2 ®iÒu kiÖn

• OR : cho phÐp d÷ liÖu tho¶ m·n 1 trong 2 ®iÒu kiÖn




Çc to¸n tö cña SQL

• [NOT] BETWEEN x AND y : [Kh«ng] lín h¬n hoÆc b»ng x vµ nhá h¬n hoÆc b»ng y.

• IN (danh s¸ch) : thuéc bÊt kú gi¸ trÞ nµo trong danh s¸ch

• x [NOT] LIKE y : §óng nÕu x [kh«ng] gièng khung mÉu y. Çc ký tù dïng trong khu«n mÉu: DÊu g¹ch d−íi ( _ ) : ChØ mét ký tù bÊt kú DÊu phÇn tr¨m ( % ) : ChØ mét nhãm ký tù bÊt kú

• IS [NOT] NULL : kiÓm tra gi¸ trÞ rçng

• EXISTS : Tr¶ vÒ TRUE nÕu cã tån t¹i.

[NOT] BETWEEN x AND y

VÝ dô chän nh©n viªn cã l−¬ng n»m trong kho¶ng 2000 vµ 3000

SELECT * FROM emp WHERE sal BETEEN 2000 AND 3000;

IN (danh s¸ch)

Chän nh©n viªn cã l−¬ng b»ng mét trong 2 gi¸ trÞ 1400 hoÆc 3000

SELECT * FROM emp WHERE sal IN (1400, 3000);

T×m tªn phßng ban nÕu phßng ®ã cã nh©n viªn lµm viÖc.

SELECT dname FROM dept WHERE EXISTS (SELECT * FROM emp WHERE dept.deptno = emp.deptno);

x [NOT] LIKE y

T×m nh©n viªn cã tªn b¾t ®Çu b»ng chuçi SMITH

SELECT * FROM emp WHERE ename LIKE 'SMITH_';

§Ó chän nh÷ng nh©n viªn cã tªn b¾t ®Çu b»ng 'SM'

SELECT * FROM emp WHERE ename LIKE 'SM%';

§Ó t×m nh÷ng nh©n viªn cã tªn cã chuçi 'A_B'

SELECT ename FROM emp WHERE ename LIKE '%A\_B%'; ESCAPE '\'

V× ký hiÖu "_" dïng ®Ó ®¹i diÖn cho mét ký tù bÊt kú nªn nÕu kh«ng cã mÖnh ®Ò ESCAPE, c©u lÖnh trªn sÏ t×m tÊt c¶ çc nh©n viªn tªn AAB, ABB, ACB, v.v... (nÕu kh«ng cã mÖnh ®Ò ESCAPE '\')

NÕu muèn ký hiÖu "_" mang ý nghÜa nguyªn thñy, tøc lµ kh«ng cßn ®¹i diÖn cho ký tù bÊt kú n÷a, ta ®Æt dÊu "\" tr−íc ký hiÖu. §ång thêi khai b¸o thªm mÖnh ®Ò ESCAPE "\"

Ta còng cã thÓ dïng mét ký tù bÊt kú thay cho "\". Ch¼ng h¹n mÖnh ®Ò sau cã cïng kÕt qu¶ víi mÖnh ®Ò trªn

SELECT ename FROM emp WHERE ename LIKE '%A^_B%'; ESCAPE '^'

Ta gäi çc ký tù nh− "\" hay "^" nãi trªn lµ çc ký tù ESCAPE.

IS [NOT] NULL

VÝ du

SELECT * FROM emp WHERE comm IS NULL ;




3.4 Bµi tËp

1. Chän nh©n viªn trong b¶ng EMP cã møc l−¬ng tõ 1000 ®Õn 2000 (chän c¸c tr−êng ENAME, DEPTNO, SAL).

ENAME DEPTNO SAL ---------- ---------- ---------- ALLEN 30 1600 WARD 30 1250 MARTIN 30 1250 TURNER 30 1500 ADAMS 20 1100 MILLER 10 1300

Sal Between 1000 to 2000

2.HiÓn thÞ m· phßng ban, tªn phßng ban, s¾p xÕp theo thø tù tªn phßng ban.

DEPTNO DNAME ------ ----------- 10 ACCOUNTING 40 OPERATIONS 20 RESEARCH 30 SALES

Order by dname

3. HiÓn thÞ danh s¸ch nh÷ng nh©n viªn lµm t¹i phßng 10 vµ 20 theo thø tù A,B,C

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ---------- ----------------- ----- ---------- ---------- ----- ----- 7876 ADAMS CLERK 7788 12-01-1983 1100 20 7782 CLARK MANAGER 7839 09-06-1981 2450 10 7902 FORD ANALYST 7566 03-12-1981 3000 20 7566 JONES MANAGER 7839 02-04-1981 2975 20 7839 KING PRESIDENT 17-11-1981 5000 10 7934 MILLER CLERK 7782 23-01-1982 1300 10 7788 SCOTT ANALYST 7566 09-12-1982 3000 20 7369 SMITH CLERK 7902 17-12-1980 800 20

Where deptno in (10,20) order by ename asc

4. HiÓn thÞ tªn vµ nghÒ nghiÖp nh÷ng nh©n viªn lµm nghÒ th− ký (clerk) t¹i phßng 20.

ENAME JOB ---------- --------- SMITH CLERK ADAMS CLERK

Where upper(job)= upper('clerk') and deptno = '20'; (l−u ý vÊn ®Ò ch÷ Hoa-th−êng)

5. HiÓn thÞ tÊt c¶ nh÷ng nh©n viªn mµ tªn cã c¸c ký tù TH vµ LL.

ENAME ---------- SMITH ALLEN MILLER

Where ename like “%TH%“ or ename like “%LL%“

6. HiÓn thÞ tªn nh©n viªn, nghÒ nghiÖp, l−¬ng cña nh÷ng nh©n viªn cã gi¸m ®èc qu¶n lý.

ENAME JOB SAL ---------- --------- ---------- SMITH CLERK 800 ALLEN SALESMAN 1600 WARD SALESMAN 1250 JONES MANAGER 2975




MARTIN SALESMAN 1250 BLAKE MANAGER 2850 CLARK MANAGER 2450 SCOTT ANALYST 3000 TURNER SALESMAN 1500 ADAMS CLERK 1100 JAMES CLERK 950 FORD ANALYST 3000 MILLER CLERK 1300 13 rows selected.

7. HiÓn thÞ tªn nh©n viªn, m· phßng ban, ngµy gia nhËp c«ng ty sao cho gia nhËp c«ng ty trong n¨m 1983.

ENAME DEPTNO HIREDATE ---------- ---------- --------- ADAMS 20 12-JAN-83

Where to_char(hiredate) like “%83“

Where hiredate like “%83“

8. HiÓn thÞ tªn nh©n viªn, l−¬ng mét n¨m (ANUAL_SAL ), th−ëng sao cho l−¬ng lín h¬n th−ëng vµ nghÒ nghiÖp lµ SALEMAN, s¾p theo thø tù l−¬ng gi¶m dÇn vµ tªn t¨ng dÇn.

ANUAL_SAL COMM ---------- ---------- 19200 300 18000 0 15000 500

4 Çc hµm ¸p dông cho 1 dßng d÷ liÖu

4.1 Çc hµm sè

§Çu vµo vµ ®Çu ra lµ çc gi¸ trÞ kiÓu sè

ROUND(n[,m]) cho gi¸ trÞ lµm trßn cña n (®Õn cÊp m, mÆc nhiªn m=0)

TRUNC(n[,m]) cho gi¸ trÞ n lÊy m ch÷ sè tÝnh tõ chÊm thËp ph©n = Format(dl, “99999,00“)

CEIL(n) cho sè nguyªn nhá nhÊt lín h¬n hoÆc b»ng n =

FLOOR(n) cho sè nguyªn lín nhÊt b»ng hoÆc nhá h¬n n =

POWER(m,n) cho lòy thõa bËc n cña m =

EXP(n) cho gi¸ trÞ cña en =

SQRT(n) cho c¨n bËc 2 cña n, n>=0 =

SIGN(n) cho dÊu cña n. =

n<0 cã SIGN(n)= -1

n=0 cã SIGN(n)= 0

n>0 cã SIGN(n)= 1

ABS(n) cho gi¸ trÞ tuyÖt ®èi =

MOD(m,n) cho phÇn d− cña phÐp chia m cho n =

Mét sè hµm kiÓu sè tham kh¶o kh¸c:

LOG(m,n) cho logarit c¬ sè m cña n =




SIN(n) cosin cña n (n tÝnh b»ng radian) =

COS(n) cho cosin cña n (n tÝnh b»ng radian) =

TAN(n) cotang cña n (n tÝnh b»ng radian) =

VÝ dô hµm ROUND(n[,m])

SELECT ROUND(4.923,1), ROUND(4.923), ROUND(4.923,-1), ROUND(4.923,2)

FROM DUMMY;

ROUND(4.923,1) ROUND(4.923) ROUND(4.923,-1) ROUND(4.923,2) -------------- ------------ --------------- -------------- 4.9 5 0 4.92

VÝ dô hµm TRUNC(n[,m])

SELECT TRUNC (4.923,1), TRUNC (4.923), TRUNC (4.923,-1), TRUNC (4.923,2)

FROM DUMMY; TRUNC(4.923,1) TRUNC(4.923) TRUNC(4.923,-1) TRUNC(4.923,2) -------------- ------------ --------------- -------------- 4.9 4 0 4.92

VÝ dô hµm CEIL(n)

SELECT CEIL (SAL), CEIL(99.9),CEIL(101.76), CEIL(-11.1) FROM EMP WHERE SAL BETWEEN 3000 AND 5000; CEIL(SAL) CEIL(99.9) CEIL(101.76) CEIL(-11.1) ---------- ---------- ------------ ----------- 5000 100 102 -11 3000 100 102 -11 3000 100 102 -11

VÝ dô hµm FLOOR(n)

SELECT FLOOR (SAL), FLOOR (99.9), FLOOR (101.76), FLOOR (-11.1) FROM EMP WHERE SAL BETWEEN 3000 AND 5000; FLOOR(SAL) FLOOR(99.9) FLOOR(101.76) FLOOR(-11.1) ---------- ----------- ------------- ------------ 5000 99 101 -12 3000 99 101 -12 3000 99 101 -12

VÝ dô hµm POWER(m,n)

SELECT SAL, POWER(SAL,2), POWER(SAL,3), POWER(50,5) FROM EMP WHERE DEPTNO =10; SAL POWER(SAL,2) POWER(SAL,3) POWER(50,5) ---------- ------------ ------------ ----------- 5000 25000000 1.2500E+11 312500000 2450 6002500 1.4706E+10 312500000 1300 1690000 2197000000 312500000

VÝ dô hµm EXP(n)

SELECT EXP(4) FROM DUMMY; EXP(4)




---------- 54.59815

VÝ dô hµm SQRT(n)

SELECT SAL, SQRT(SAL), SQRT(40), SQRT (COMM) FROM EMP WHERE DEPTNO =10; SAL SQRT(SAL) SQRT(40) SQRT(COMM) ---------- ---------- ---------- ---------- 5000 70.7106781 6.32455532 2450 49.4974747 6.32455532 1300 36.0555128 6.32455532

VÝ dô hµm SIGN(n)

SELECT SAL-NVL(COMM,0), SIGN(SAL-NVL(COMM,0)), NVL(COMM,0)-SAL, SIGN(NVL(COMM,0)-SAL) FROM EMP WHERE DEPTNO =30 SAL-NVL(COMM,0)SIGN(SAL-NVL(COMM,0))NVL(COMM,0)-SAL SIGN(NVL(COMM,0)-SAL) --------------- ----------- --------------- --------------------- 2850 1 -2850 -1 -150 -1 150 1 1300 1 -1300 -1 1500 1 -1500 -1 950 1 -950 -1 750 1 -750 -1

4.2 Çc hµm ký tù

CONCAT(char1, char2) cho kÕt hîp cña 2 chuçi ký tù, t−¬ng tù nh− sö dông to¸n tö ||

INITCAP(char) cho chuçi víi ký tù ®Çu çc tõ lµ ký tù hoa

LOWER(char) cho chuçi ký tù viÕt th−êng (kh«ng viÕt hoa)

LPAD(char1, n [,char2]) cho chuçi ký tù cã chiÒu dµi b»ng n. NÕu chuçi char1 ng¾n h¬n n th× thªm vµo bªn tr¸i chuçi char2 cho ®ñ n ký tù. NÕu chuçi char1 dµi h¬n n th× gi÷ l¹i n ký tõ tÝnh tõ tr¸i sang

LTRIM(char1, n [,char2]) bá çc ký tù trèng bªn tr¸i

NLS_INITCAP(char) cho chuçi víi ký tù ®Çu çc tõ lµ ch÷ hoa, çc ch÷ cßn l¹i lµ ch÷ th−êng

REPLACE(char,search_string[,replacement_string]) : thay tÊt c¶ çc chuçi search_string cã trong chuçi char b»ng chuçi replacement_string.

RPAD(char1, n [,char2]) Gièng LPAD(char1, n [,char2]) nh−ng c¨n ph¶i

RTRIM(char1, n [,char2]) bá çc ký tù trèng bªn ph¶i

SOUNDEX(char) cho chuçi ®ång ©m cña char.

SUBSTR(char, m [,n]) cho chuçi con cña chuçi char lÊy tõ vÞ trÝ m vÕ ph¶i n ký tù, nÕu kh«ng chØ n th× lÊy cho ®Õn cuèi chuçi

TRANSLATE(char, from, to) cho chuçi trong ®ã mçi ký tù trong chuçi from thay b»ng ký tù t−¬ng øng trong chuçi to, nh÷ng ký tù trong chuçi from kh«ng cã t−¬ng øng trong chuçi to sÏ bÞ lo¹i bá.

UPPER(char) cho chuçi ch÷ hoa cña chuçi char




ASCII(char) cho ký tù ASCII cña byte ®Çu tiªn cña chuçi char

INSTR(char1, char2 [,n[,m]]) t×m vÞ trÝ chuçi char2 trong chuçi char1 b¾t ®Çu tõ vÞ trÝ n, lÇn xuÊt hiÖn thø m.

LENGTH(char) cho chiÒu dµi cña chuçi char

VÝ dô hµm LOWER(char)

SELECT LOWER(DNAME), LOWER(‘SQL COURSE’) FROM DEPT; LOWER(DNAME) LOWER('SQL -------------- ---------- accounting sql course research sql course sales sql course operations sql course

VÝ dô hµm UPPER(char)

SELECT ENAME FROM EMP WHERE ENAME = UPPER(‘Smith’); ENAME ---------- SMITH

VÝ dô hµm INITCAP(char)

SELECT INITCAP(DNAME), INITCAP(LOC) FROM DEPT; INITCAP(DNAME) INITCAP(LOC) -------------- ------------- Accounting New York Research Dallas Sales Chicago Operations Boston

VÝ dô hµm CONCAT(char1, char2)

SELECT CONCAT(ENAME, JOB) JOB FROM EMP WHERE EMPNO = 7900; JOB ------------------- JAMES CLERK

VÝ dô hµm LPAD(char1, n [,char2])

SELECT LPAD(DNAME,20,’*’), LPAD(DNAME,20), LPAD(DEptno,20,’ ’) FROM DEPT; LPAD(DNAME,20,'*') LPAD(DNAME,20) LPAD(DEPTNO,20,'') -------------------- -------------------- -------------------- ******ACCOUNTING ACCOUNTING 10 ******RESEARCH RESEARCH 20 ******SALES SALES 30 ******OPERATIONS OPERATIONS 40

VÝ dô hµm RPAD(char1, n [,char2])

SELECT RPAD(DNAME,20,’*’), RPAD(DNAME,20), RPAD(DEptno,20,’ ’) FROM DEPT;




RPAD(DNAME,20,'*') RPAD(DNAME,20) RPAD(DEPTNO,20,'') -------------------- -------------------- -------------------- ACCOUNTING ****** ACCOUNTING 10 RESEARCH ****** RESEARCH 20 SALES ****** SALES 30 OPERATIONS ****** OPERATIONS 40

VÝ dô hµm SUBSTR(char, m [,n])

SELECT SUBSTR(‘ORACLE’,2,4), SUBSTR(DNAME,2), SUBSTR(DNAME,3,5) FROM DEPT; SUBS SUBSTR(DNAME, SUBST ---- ------------- ----- RACL CCOUNTING COUNT RACL ESEARCH SEARC RACL ALES LES RACL PERATIONS ERATI

VÝ dô hµm INSTR(char1, char2 [,n[,m]])

SELECT DNAME, INSTR(DNAME, ‘A’), INSTR(DNAME,’ES’), INSTR(DNAME,’C’,1,2) FROM DEPT; DNAME INSTR(DNAME,'A') INSTR(DNAME,'ES') INSTR(DNAME,'C',1,2) -------------- ---------------- ----------------- -------------------- ACCOUNTING 1 0 3 RESEARCH 5 2 0 SALES 2 4 0 OPERATIONS 5 0 0

VÝ dô hµm LTRIM(char1, n [,char2])

SELECT DNAME, LTRIM(DNAME,’A’), LTRIM(DNAME,’AS’), LTRIM(DNAME,’ASOP’) FROM DEPT; DNAME LTRIM(DNAME,'A LTRIM(DNAME,'A LTRIM(DNAME,'A -------------- -------------- -------------- -------------- ACCOUNTING CCOUNTING CCOUNTING CCOUNTING RESEARCH RESEARCH RESEARCH RESEARCH SALES SALES LES LES OPERATIONS OPERATIONS OPERATIONS ERATIONS

VÝ dô hµm RTRIM(char1, n [,char2])

SELECT DNAME, RTRIM(DNAME,’A’), RTRIM(DNAME,’AS’), RTRIM(DNAME,’ASOP’) FROM DEPT; DNAME RTRIM(DNAME,'A RTRIM(DNAME,'A RTRIM(DNAME,'A -------------- -------------- -------------- -------------- ACCOUNTING ACCOUNTING ACCOUNTING ACCOUNTING RESEARCH RESEARCH RESEARCH RESEARCH SALES SALES SALES SALES OPERATIONS OPERATIONS OPERATIONS OPERATIONS

VÝ dô hµm SOUNDEX(char)

SELECT ENAME, SOUNDEX(ENAME) FROM EMP WHERE SOUNDEX(ENAME)= SOUNDEX(‘FRED’); ENAME SOUN ---------- ---- FORD F630

VÝ dô hµm LENGTH(char)

SELECT LENGTH(‘SQL COURSE’), LENGTH(DEPTNO), LENGTH(DNAME) FROM DEPT;




LENGTH('SQLCOURSE') LENGTH(DEPTNO) LENGTH(DNAME) ------------------- -------------- ------------- 10 2 14 10 2 14 10 2 14 10 2 14

VÝ dô hµm TRANSLATE(char, from, to)

SELECT ENAME, TRANSLATE(ENAME,'C','F'), JOB, TRANSLATE(JOB,'AR','IT') FROM EMP WHERE DEPTNO = 10; ENAME TRANSLATE( JOB TRANSLATE ---------- ---------- --------- --------- KING KING PRESIDENT PTESIDENT CLARK FLARK MANAGER MINIGET MILLER MILLER CLERK CLETK

VÝ dô hµm REPLACE(char,search_string[,replacement_string])

SELECT JOB, REPLACE(JOB, ‘SALESMAN’, ‘SALESPERSON’), ENAME, REPLACE(ENAME, ‘CO’,’PR’) FROM EMP WHERE DEPTNO =30 OR DEPTNO =20; JOB REPLACE(JOB,'SALESMAN', ENAME REPLACE(ENAME,'CO',' --------- ----------------------- --------- --------------- MANAGER MANAGER BLAKE BLAKE MANAGER MANAGER JONES JONES SALESMAN SALESPERSON MARTIN MARTIN SALESMAN SALESPERSON ALLEN ALLEN SALESMAN SALESPERSON TURNER TURNER CLERK CLERK JAMES JAMES SALESMAN SALESPERSON WARD WARD ANALYST ANALYST FORD FORD CLERK CLERK SMITH SMITH ANALYST ANALYST SCOTT SPRTT CLERK CLERK ADAMS ADAMS

VÝ dô c¸c hµm lång nhau:

SELECT DNAME, LENGHT(DNAME), LENGHT(TRANSLATE,DNAME, ‘AS’,’A’)) FROM DEPT; DNAME LENGTH(DNAME) LENGTH(TRANSLATE(DNAME,'AS','A')) -------------- ------------- --------------------------------- ACCOUNTING 14 14 RESEARCH 14 13 SALES 14 12 OPERATIONS 14 13

4.3 C¸c hµm ngµy

MONTH_BETWEEN(d1, d2) cho biÕt sã th¸ng gi÷a ngµy d1 vµ d2.

ADD_MONTHS(d,n) cho ngµy d thªm n th¸ng.

NEXT_DAY(d, char ) cho ngµy tiÕp theo ngµy d cã thø chØ bëi char.

LAST_DAY(d) cho ngµy cuèi cïng trong th¸ng chØ bëi d.

VÝ dô hµm MONTH_BETWEEN(d1, d2)

SELECT MONTHS_BETWEEN( SYSDATE, HIREDATE), MONTHS_BETWEEN('01-01-2000','05-10-2000')




FROM EMP WHERE MONTHS_BETWEEN( SYSDATE,HIREDATE)>240; MONTHS_BETWEEN(SYSDATE,HIREDATE) TWEEN('01-01-2000','05-10-2000') -------------------------------- -------------------------------- 241.271055 -9.1290323 241.206539 -9.1290323 243.367829 -9.1290323

VÝ dô hµm ADD_MONTHS(d,n)

SELECT HIREDATE, ADD_MONTHS(HIRE,3), ADD_MONTHS(HIREDATE,-3) FROM EMP WHERE DEPTNO=20; HIREDATE ADD_MONTHS ADD_MONTHS ---------- ---------- ---------- 02-04-1981 02-07-1981 02-01-1981 03-12-1981 03-03-1982 03-09-1981 17-12-1980 17-03-1981 17-09-1980 09-12-1982 09-03-1983 09-09-1982 12-01-1983 12-04-1983 12-10-1982

VÝ dô hµm NEXT_DAY(d, char )

SELECT HIREDATE, NEXT_DAY(HIREDATE,’FRIDAY’), NEXT_DAY(HIREDATE,6) FROM EMP WHERE DEPTNO = 10; HIREDATE NEXT_DAY(H NEXT_DAY(H ---------- ---------- ---------- 17-11-1981 20-11-1981 20-11-1981 09-06-1981 12-06-1981 12-06-1981 23-01-1982 29-01-1982 29-01-1982

VÝ dô hµm LAST_DAY(d)

SELECT SYSDATE, LAST_DAY(SYSDATE), HIREDATE, LAST_DAY(HIREDATE), LAST_DAY(’15-01-2001’) FROM EMP WHERE DEPTNO =20; SYSDATE LAST_DAY(S HIREDATE LAST_DAY(H LAST_DAY(' ---------- ---------- ---------- ---------- ---------- 28-03-2001 31-03-2001 02-04-1981 30-04-1981 31-01-2001 28-03-2001 31-03-2001 03-12-1981 31-12-1981 31-01-2001 28-03-2001 31-03-2001 17-12-1980 31-12-1980 31-01-2001 28-03-2001 31-03-2001 09-12-1982 31-12-1982 31-01-2001 28-03-2001 31-03-2001 12-01-1983 31-01-1983 31-01-2001

Mét sè hµm kh¸c cã thÓ ¸p dông cho kiÓu ngµy:

ROUND(date1) tr¶ vÒ ngµy date 1 t¹i thêi ®iÓm gi÷a tr−a 12:00 AM

ROUND(date1,’MONTH’) NÕu date 1 n»m trong nöa th¸ng ®Çu tr¶ vÒ ngµy ®Çu tiªn cña thµng, ng−îc l¹i sÏ tr¶ vÒ ngµy ®Çu tiªn cña th¸ng sau.

ROUND(date1,’YEAR’) NÕu date 1 n»m trong nöa n¨m ®Çu tr¶ vÒ ngµy ®Çu tiªn cña thµng, ng−îc l¹i sÏ tr¶ vÒ ngµy ®Çu tiªn cña n¨m sau.

TRUNC(date1, ’MONTH’) Tr¶ vÒ ngµy ®Çu tiªn cña th¸ng chøa date1

TRUNC(date1, ’YEAR’) Tr¶ vÒ ngµy ®Çu tiªn cña n¨m chøa date1




4.4 C¸c hµm chuyÓn ®æi kiÓu

TO_CHAR(number|date, ‘fmt’) ChuyÓn kiÓu sè vµ ngµy vÒ kiÓu ký tù.

TO_NUMBER(char) ChuyÓn ký tù cã néi dung sè sang sè

TO_DATE(‘chsr’,’fmt’) ChuyÓn ký tù sang kiÓu ngµy víi ®Þnh d¹ng ®Æt trong fmt.

DECODE(EXPR, SEARCH1, RESULT1, SEARCH2, RESULT2, DEFAULT):

So s¸nh biÓu thøc expr víi gi¸ trÞ search nÕu ®óng tr¶ vÒ gi¸ trÞ result nÕu kh«ng tr¶ vÒ gi¸ trÞ default.

NVL(COL|VALUE, VAL) ChuyÓn gi¸ trÞ COL|VALUE thµnh val nÕu null.

Greatest(col|value1, col|value2) Tr¶ gi¸ trÞ lín nhÊt trong d·y gi¸ trÞ.

Vd:

SELECT To_char (sysdate, ‘day, ddth month yyyy’) from dummy; SELECT EMPNO, ENAME, HIREDATE FROM EMP WHERE HIREDATE = TO_DATE (‘June 4, 1984’, ‘month dd, yyyy’); INSERT INTO EMP (EMPNO, DEPTNO, HIREDATE VALUES (777, 20, TO_DATE(’19-08-2000’, ‘DD-MM-YYYY’); SELECT ENAME, JOB, DECODE (JOB, ‘CLERK’,’WWORKER’,’MANAGER’,’BOSS’,’UNDEFINED’) DECODÑD_JOB FROM EMP; SELECT GREATEST(1000,2000), GREATEST(SAL,COMM) FROM EMP WHERE DEPTNO = 10;

Mét sè khu«n d¹ng ngµy

SCC hoÆc CC thÕ kû; S chØ ngµy BC YYYY hoÆc SYYYY n¨m; S chØ ngµy BC YYY, YY, Y ChØ n¨m víi 3,2,1 ký tù sè IYYY, IYY, IY, I ChØ n¨m theo chuÈn ISO SYEAR, YEAR ChØ n¨m theo c¸ch ph¸t ©m cña ng−êi anh; Q Quý trong n¨m MM Gi¸ trÞ th¸ng víi 2 sè (01-12) MONTH Tªn ®Çy ®ñ cña th¸ng theo tiÕng anh, ®ä dµi 9 MON Th¸ng víi 3 ký tù viÕn t¾t (JAN, FEB...) WW, W TuÇn trong n¨m hoÆc trong th¸ng DDD, DD, D Ngµy trong n¨m, th¸ng hoÆc tuÇn DAY ChØ thø trong tuÇn DY ChØ thø trong tuÇn víi 3 ký tù viÕt t¾t J Ngµy Julian; b¾t ®Çu tõ ngµy 31/12/4713 tr−íc c«ng

nguyªn AM, PM ChØ ®Þnh s¸ng, chiÒu HH, HH12 HH24 ChØ giê trong ngµy (1-12) hoÆc (0-23) MI Phót (0-59) SS Gi©y (0-59) SSSSS Sè gi©y ®Õn nöa ®ªm (0-86399) / . , - ®−îc tù ®éng thªm khi ®Æt trong khu«n d¹ng “char” §o¹n ký tù ®Æt trong nh¸y ®óp ®−îc tù ®éng thªm khi ®Æt

trong khu«n d¹ng TH Thªm phÇn thø tù (1st, 2nd, 4th ) SP Ph¸t ©m sè ( FOUR víi DDSP)




SPTH, THSP Ph¸t ©m vµ chuyÓn sang d¹ng thø tù ( First, second, ...)

RR Ngµy chuyÓn giao thiªn niªn kû víi çc n¨m <1999. N¨m

0-49 50-99

N¨m hiÖn t¹i

0-49 thÕ kû hiÖn t¹i

ThÕ kû sau

50-99 ThÕ kû tr−íc

ThÓ kû hiÖn t¹i

Mét sè khu«n d¹ng sè

Ký tù

M« t¶ VÝ dô KÕt qu¶

9 X¸c ®Þnh hiÓn thÞ 1 sè 999999 1234 0 HiÓn thÞ c¶ sè 0 ë ®Çu nÕu ®é

dµi khu«n d¹ng lín h¬n sè hiÖn cã

099999 001234

$ Thªm ký tù tiÒn tÖ $999999 $1234 L Thªm ký tù tiÒn tÖ b¶n ®Þa L999999 FF1234 . DÊu thËp ph©n 999999.99 1234.00 , DÊu ph©n çch phÇn ngh×n 999,999 1,234 MI DÊu ©m ë bªn ph¶i ( víi çc

gi¸ trÞ ©m) 999999MI 1234-

PR Thªm ngoÆc nhän vµo çc gi¸ trÞ ©m

999999PR <1234>

EEE ChuyÓn sang hiÓn thÞ sè E 99.9999RRRR 1.234E+03 V Nh©n víi 10 n, n lµ sè çc sè

9 ®Æt sau V 9999V99 123400

B HiÓn thÞ c¶ gi¸ trÞ 0 nÕu = 0.

B9999.99 1234.00

4.5 Bµi tËp

1. LiÖt kª tªn nh©n viªn, m· phßng ban vµ l−¬ng nh©n viªn ®−îc t¨ng 15% (PCTSAL).

DEPTNO ENAME PCTSAL ---------- ---------- ---------- 10 KING 5000 30 BLAKE 2850 10 CLARK 2450 20 JONES 2975 30 MARTIN 1250 30 ALLEN 1600 30 TURNER 1500 30 JAMES 950 30 WARD 1250 20 FORD 3000 20 SMITH 800 20 SCOTT 3000 20 ADAMS 1100 10 MILLER 1300

2. ViÕt c©u lÖnh hiÓn thÞ nh− sau:

EMPLOYEE_AND_JOB -------------------- KING*******PRESIDENT BLAKE********MANAGER CLARK********MANAGER JONES********MANAGER MARTIN******SALESMAN ALLEN*******SALESMAN TURNER******SALESMAN JAMES**********CLERK WARD********SALESMAN FORD*********ANALYST




SMITH**********CLERK SCOTT********ANALYST ADAMS**********CLERK MILLER*********CLERK


EMPLOYEE ----------------- KING (President) BLAKE (Manager) CLARK (Manager) JONES (Manager) MARTIN (Salesman) ALLEN (Salesman) TURNER (Salesman) JAMES (Clerk) WARD (Salesman) FORD (Analyst) SMITH (Clerk) SCOTT (Analyst) ADAMS (Clerk) MILLER (Clerk)


ENAME DEPTNO JOB ---------- ---------- --------------- BLAKE 30 Manager MARTIN 30 Salesperson ALLEN 30 Salesperson TURNER 30 Salesperson JAMES 30 Clerk WARD 30 Salesperson

5. T×m ngµy thø 6 ®Çu tiªn c¸ch 2 th¸ng so víi ngµy hiÖn t¹i hiÓn thÞ ngµy d−íi d¹ng 09 February 1990.

6. T×m th«ng itn vÒ tªn nh©n viªn, ngµy gia nhËp c«ng ty cña nh©n viªn phßng sè 20, sao cho hiÓn thÞ nh− sau:

ENAME DATE_HIRED ---------- -------------------------- JONES april,SECOND 1981 FORD december,THIRD 1981 SMITH december,SEVENTEENTH 1980 SCOTT december,NINTH 1982 ADAMS january,TWELFTH 1983

7. HiÓn thÞ tªn nh©n viªn, ngµy gia nhËp c«ng ty, ngµy xÐt n©ng l−¬ng (sau ngµy gia nhËp c«ng ty 1 n¨m), s¾p xÕp theo thø tù ngµy xÐt n©ng l−¬ng.

ENAME HIREDATE REVIEW ---------- ---------- ---------- SMITH 17-12-1980 17-12-1981 ALLEN 20-02-1981 20-02-1982 WARD 22-02-1981 22-02-1982 JONES 02-04-1981 02-04-1982 BLAKE 01-05-1981 01-05-1982 CLARK 09-06-1981 09-06-1982 TURNER 08-09-1981 08-09-1982 MARTIN 28-09-1981 28-09-1982 KING 17-11-1981 17-11-1982 JAMES 03-12-1981 03-12-1982 FORD 03-12-1981 03-12-1982 MILLER 23-01-1982 23-01-1983 SCOTT 09-12-1982 09-12-1983 ADAMS 12-01-1983 12-01-1984

8.HiÓn thÞ tªn nh©n viªn vµ l−¬ng d−íi d¹ng




ENAME SALARY ---------- ------------ ADAMS BELOW 1500 ALLEN 1600 BLAKE 2850 CLARK 2450 FORD 3000 JAMES BELOW 1500 JONES 2975 KING 5000 MARTIN BELOW 1500 MILLER BELOW 1500 SCOTT 3000 SMITH BELOW 1500 TURNER On Target WARD BELOW 1500

9. Cho biÕt thø cña ngµy hiÖn t¹i

10. §−a chuçi d−íi d¹ng nn/nn, kiÓm tra nÕu khóng khu«n d¹ng tr¶ lêi lµ YES, ng−îc l¹i lµ no. KiÓm tra víi c¸c chuçi 12/34, 01/1a, 99\88

VALUE VALID? ----- ------- 12/34 YES

11. HiÓn thÞ tªn nh©n viªn, ngµy gia nhËp c«ng ty, ngµy lÜnh l−¬ng sao cho ngµy lÜnh l−¬ng ph¶i vµo thø 6, nh©n viªn chØ ®−îc nhËn l−¬ng sau Ýt nhÊt 15 ngµy lµm viÖc t¹i c«ng ty, s¾p xÕp theo thø tù ngµy gia nhËp c«ng ty.

5 BiÕn runtime

D÷ liÖu thay thÕ trong c©u lÖnh

Dïng (&) ®Ó chØ phÇn thay thÕ trong c©u lÖnh.

NÕu dïng (&&) chØ biÕn thay thÕ th× sau c©u lÖnh biÕn thay thÕ vÉn cßn tån t¹i

VÝ dô

SELECT * FROM emp WHERE &Condition Enter value for condition: sal > 1000 Khi Êy c©u lÖnh trªn t−¬ng ®−¬ng

SELECT * FROM emp

WHERE sal > 1000

VÝ du 2:

Select ename, deptno, job From emp Where deptno = &&depno_please;

LÖnh Define

Khai b¸o vµ g¸n trÞ cho c¸c biÕn, vÝ dô khai b¸o biÕn condition cã tri 'sal > 1000'

DEFINE condition = 'sal > 1000'

Khi ®ã c©u lÖnh sau kh«ng yªu cÇu nhËp vµo gi¸ trÞ cho codition

SELECT * FROM emp WHERE &Condition




§Ó lo¹i bá biÕn ra khái bé nhí dïng lÖnh UNDEFINE, vÝ dô

UNDEFINE condition

§Ó liÖt kª çc biÕn ®· khai b¸o dïng lÖnh DEFINE mµ kh«ng chØ biÕn, vÝ dô

DEFINE DEFINE CONDITION = 'SAL > 1000'

VÝ dô:

DEFINE REM=’SAL*12+NVL(COMM,0)’ SELECT ENAME, JOB, &REM FROM EKP ORDER BY & REM;

LÖnh Accept

Khai b¸o vµ g¸n trÞ cho biÕn víi dßng hiÓn thÞ

ACCEPT variable [NUMBER/CHAR] [PROMPT/NOPROMPT 'text'] HIDE

VÝ dô

ACCEPT Salary NUMBER PROMPT 'Salary figure: ' Salary figure : 3000

Tõ kho¸ hide cho phÐp che chuçi nhËp liÖu, hay dïng khi nhËp password.

ACCEPT password CHAR PROMPT 'Enter password: ' HIDE Password : ******

5.1 Bµi tËp

1. HiÓn thÞ tªn nh©n viªn, ngµy gia nhËp c«ng ty víi ®iÒu kiÖn ngµy gia nhËp c«ng ty n»m trong kho¶ng hai biÕn runtime ®−îc nhËp vµo tõ bµn phÝm (&first_date, &last_date).

2. HiÓn thÞ tªn nh©n viªn, nghÒ nghiÖp, l−¬ng, m· gi¸m ®èc, m· phßng ban víi ®iÒu kiÖn nghÒ nghiÖp b»ng mét biÕn ®−îc nhËp vµo tõ bµn phÝm. (&job)

3. §Þnh nghÜa mét biÕn tÝnh thu nhËp mét n¨m cña nh©n viªn. Dïng biÕn nµy ®Ó t×m nh÷ng nh©n viªn cã thu nhËp lín h¬n hoÆc b»ng $30000.

4. §Þnh nghÜa mét biÕn lµ kho¶ng thêi gian nh©n viªn lµm trong c«ng ty. HiÓn thÞ tªn nh©n viªn vµ qu·ng thêi gian nh©n viªn ®ã lµm viÖc víi ®iÒu kiÖn nh©n viªn lµ mét biÕn ®−îc nhËp vµo tõ bµn phÝm.

ENAME LENGTH OF SERVICE ---------- --------------------- KING 19 YEAR 4 MONTHS

6 Çc hµm nhãm ¸p dông cho lín h¬n hoÆc b»ng 1 dßng d÷ liÖu

6.1 Çc hµm t¸c ®éng trªn nhãm

Çc hµm t¸c ®éng trªn nhãm çc dßng d÷ liÖu t¸c ®éng lªn mét tËp hîp çc çc dßng d÷ liÖu. Gåm çc hµm:

AVG([DISTINCT/ALL] n) Gi¸ trÞ trung b×nh cña n,kh«ng kÓ trÞ null

COUNT([DISTINCT/ALL] expr) Sè row cã expr kh¸c null

MAX([DISTINCT/ALL] expr) Gi¸ trÞ lín nhÊt cña expr

MIN([DISTINCT/ALL] expr) Gi¸ trÞ nhá nhÊt cña expr

STDDVE([DISTINCT/ALL] n) Ph−¬ng sai cña n kh«ng kÓ trÞ null




SUM([DISTINCT/ALL] n) Tæng cña cña n kh«ng kÓ trÞ null

VARIANCE([DISTINCT/ALL] n) Variance cña n kh«ng kÓ trÞ null

Chó ý tÊt c¶ çc hµm trªn nhãm mÉu tin ®Òu bá qua gi¸ trÞ NULL trõ hµm COUNT. Dïng hµm NVL ®Ó chuyÓn ®æi vµ tÝnh gi¸ trÞ NULL.

Cã 2 çch ®Ó dïng çc çc hµm nµy

• T¸c ®éng trªn toµn bé çc dßng d÷ liÖu cña c©u lÖnh truy vÊn

• T¸c ®éng trªn mét nhãm d÷ liÖu cïng tÝnh chÊt cña c©u lÖnh truy vÊn. Cïng tÝnh chÊt ®−îc chØ bëi mÖnh ®Ò

[GROUP BY expr] [HAVING condition]




VÝ dô T¸c ®éng trªn toµn bé çc dßng d÷ liÖu cña c©u lÖnh truy vÊn:

Select AVG(SAL) FROM EMP: /TÝnh møc l−¬ng trung b×nh cña toµn bé nh©n viªn / Select MIN(SAL) FROM EMP WHERE JOB =’CLERK’: /TÝnh møc l−¬ng thÊp nhÊt cña nh©n viªn lµm nghÒ CLERK /

VÝ dô t¸c ®éng trªn mét nhãm d÷ liÖu cïng tÝnh chÊt cña c©u lÖnh truy vÊn.

SELECT JOB, AVG(SAL) FROM EMP GROUP BY JOB; / TÝnh møc l−¬ng trung b×nh cña tõng lo¹i nghÒ nghiÖp/

Chó ý: ChØ ®−îc cïng ®Æt trong mÖnh ®Ó SELECT çc hµm nhãm hoÆc çc column ®· ®Æt trong mÖnh ®Ò GROUP BY. VÝ dô

§óng: SELECT MAX(SAL), JOB FROM EMP GROUP BY JOB; Sai: SELECT MAX(SAL), JOB FROM EMP;

6.2 MÖnh ®Ò GROUP BY

Có ph¸p:

SELECT [DISTINCT ] {*, column [alias],...} FROM table; [WHERE condition] [GROUP BY expr] [GROUP BY expr] [GROUP BY expr] [GROUP BY expr] [H[H[H[HAVING condition]AVING condition]AVING condition]AVING condition] [ORDER BY expr/position [DESC/ASC]]

MÖnh ®Ò GROUP BY sÏ nhãm çc dßng d÷ liÖu cã cïng gi¸ trÞ cña expr. VÝ dô GROUP BY JOB nghÜa lµ sÏ nhãm çc nghÒ gièng nhau.

MÖnh ®Ò HAVING lµ ®Æt ®iÒu kiÖn cña nhãm d÷ liÖu. MÖnh ®Ò nµy kh¸c mÖnh ®Ò WHERE ë chç mÖnh ®Ò WHERE ®Æt ®iÒu kiÖn cho toµn bé c©u lÖnh SELECT. VÝ dô:

SELECT JOB, MAX(SAL) FROM EMP WHERE JOB !=’MANAGER’ GROUP BY JOB; JOB MAX(SAL) --------- ---------- ANALYST 3000 CLERK 1300 PRESIDENT 5000 SALESMAN 1600 SELECT JOB, MAX(SAL) FROM EMP GROUP BY JOB HAVING COUNT(*)>3; JOB MAX(SAL) --------- ---------- CLERK 1300 SALESMAN 1600 SELECT JOB, MAX(SAL) FROM EMP




HAVING MAX(SAL)>=3000 GROUP BY JOB; JOB MAX(SAL) --------- ---------- ANALYST 3000 PRESIDENT 5000

6.3 Bµi tËp

1. T×m l−¬ng thÊp nhÊt, lín nhÊt vµ l−¬ng trung b×nh cña tÊt c¶ çc nh©n viªn

2. t×m l−¬ng nhá nhÊt vµ lín cña mçi lo¹i nghÒ nghiÖp

3. T×m xem cã bao nhiªu gi¸m ®èc trong danh s¸ch nh©n viªn.

4. T×m tÊt c¶ çc phßng ban mµ sè nh©n viªn trong phßng >3

5. T×m ra møc l−¬ng nhá nhÊt cña mçi nh©n viªn lµm viÖc cho mét gi¸m ®èc nµo ®ã s¾p xÕp theo thø tù t¨ng dÇn cña møc l−¬ng.

7 HiÓn thÞ néi dung d÷ liÖu tõ nhiÒu b¶ng

7.1 Mèi liªn kÕt t−¬ng ®−¬ng

• Mèi liªn kÕt t−¬ng ®−¬ng ®−îc thÓ hiÖn trong mÖnh ®Ó WHERE.

• §Ó liªn kÕt trong mÖnh ®Ó WHERE ph¶i chØ râ tªn cña çc column vµ mÖnh ®Ò ®−îc ®Æt t−¬ng ®−¬ng.

Vd: emp.deptno =dept.deptno

• Çc column trïng tªn ph¶i ®−îc chØ râ column ®ã n»m ë b¶ng n¶o th«ng qua tªn hoÆc qua alias. Tªn trïng nµy cã thÓ ®Æt trong çc mÖnh ®Ò kh¸c nh− SELECT, ORDER BY..

Vd: SELECT DEPT.DEPTNO, ENAME,JOB, DNAME FROM EMP, DEPT WHERE EMP.DEPTNO = DEPT.DEPTNO ORDER BY DEPT.DEPTNO; SELECT A.DEPTNO, A.ENAME, A.JOB, B.DNAME FROM EMP A, DEPT B WHERE A.DEPTNO = B.DEPTNO ORDER BY A.DEPTNO;

7.2 Mèi liªn kÕt kh«ng t−¬ng ®−¬ng

• Mèi liªn kÕt t−¬ng ®−¬ng ®−îc thÓ hiÖn trong mÖnh ®Ó WHERE.

• §Ó liªn kÕt trong mÖnh ®Ó WHERE ph¶i chØ râ tªn cña çc column vµ mÖnh ®Ò ®−îc ®Æt KH¤NG t−¬ng ®−¬ng.

Vd: WHERE E.SAL BETWEEN S. LOSAL AND S.HISAL

• Çc column trïng tªn ph¶i ®−îc chØ râ column ®ã n»m ë b¶ng nµo th«ng qua tªn hoÆc qua alias. Tªn trïng nµy cã thÓ ®Æt trong çc mÖnh ®Ò kh¸c nh− SELECT, ORDER BY..

VD: SELECT E.ENAME,E.JOB, S.GRADE FROM EMP E, SALGRADE S WHERE E.SAL BETWEEN S. LOSAL AND S.HISAL;

§iÒu kiÖn liªn kÕt ®óng lµ sè çc b¶ng - 1 = sè çc ®iÒu kiÖn liªn kÕt




7.3 Mèi liªn kÕt céng

• Mèi liªn kÕt céng tr¶ vÒ c¶ çc gi¸ trÞ NULL trong biÓu thøc ®iÒu kiÖn. DÊu (+) ®Ó ë vÕ nµo tÝnh thªm çc gi¸ trÞ NULL ë vÕ ®ã.

• Mét c©u lÖnh select chØ ®Æt ®−îc 1 mèi liªn kÕt céng, dÊu (+) ®Æt ë bªn ph¶i column liªn kÕt

• Trong mÖnh ®Ò WHERE cña mèi liªn kÕt céng kh«ng ®−îc dïng to¸n tö IN hoÆc OR ®Ó nèi çc ®iÒu kiÖn liªn kÕt kh¸c.

Vd: SELECT E.ENAME, D.DEPTNO, D.DNAME FROM EMP E, DEPT D WHERE E.DEPTNO (+)=D.DEPTNO AND D.DEPTNO IN (30, 40); ENAME DEPTNO DNAME ---------- ---------- ------------- BLAKE 30 SALES MARTIN 30 SALES ALLEN 30 SALES TURNER 30 SALES JAMES 30 SALES WARD 30 SALES 40 OPERATIONS

7.4 Liªn kÕt cña b¶ng víi chÝnh nã

Cã thÓ liªn kÐt b¶ng víi chÝnh nã b»ng çch ®Æt alias. VÝ du:

Select e.ename emp_name, e.sal emp_sal, m.ename mgr_name, m.sal mgr_sal from emp e, emp m where e.mgr = m.empno and e.sal <m.sal; EMP_NAME EMP_SAL MGR_NAME MGR_SAL ---------- ---------- ---------- ---------- BLAKE 2850 KING 5000 CLARK 2450 KING 5000 JONES 2975 KING 5000 MARTIN 1250 BLAKE 2850 ALLEN 1600 BLAKE 2850 TURNER 1500 BLAKE 2850 JAMES 950 BLAKE 2850 WARD 1250 BLAKE 2850 SMITH 800 FORD 3000 ADAMS 1100 SCOTT 3000 MILLER 1300 CLARK 2450

7.5 Çc to¸n tö tËp hîp

UNION KÕt hîp kÕt qu¶ cña nhiÒu c©u hái víi nhau, chØ gi÷ l¹i mét ®¹i diÖn cho çc mÉu tin trïng nhau.

UNION ALL KÕt hîp kÕt qu¶ cña nhiÒu c©u hái víi nhau, çc mÉu tin trïng nhau còng ®−îc lÆp l¹i

INTERSET LÊy phÇn giao çc kÕt qu¶ cña nhiÒu c©u hái

MINUS LÊy kÕt qu¶ cã trong c©u hái thø nhÊt mµ kh«ng cã trong c©u hái thø hai (c©u hái sau to¸n tö MINUS)

Vd: Select job from emp where deptno = 10 Union Select job from emp where deptno = 30;




JOB --------- CLERK MANAGER PRESIDENT SALESMAN

7.6 Bµi tËp

1. HiÓn thÞ toµn bé tªn nh©n viªn vµ tªn phßng ban lµm viÖc s¾p xÕp theo tªn phßng ban.

2. HiÓn thÞ tªn nh©n viªn, vÞ trÝ ®Þa lý, tªn phßng víi ®iÒu kiÖn l−¬ng >1500.

ENAME LOC DNAME ---------- ------------- ----------- KING NEW YORK ACCOUNTING BLAKE CHICAGO SALES CLARK NEW YORK ACCOUNTING JONES DALLAS RESEARCH ALLEN CHICAGO SALES FORD DALLAS RESEARCH SCOTT DALLAS RESEARCH

3. HiÓn thÞ tªn nh©n viªn, nghÒ nghiÖp, l−¬ng vµ møc l−¬ng.

ENAME JOB SAL GRADE ---------- --------- ---------- ---------- JAMES CLERK 950 1 SMITH CLERK 800 1 ADAMS CLERK 1100 1 MARTIN SALESMAN 1250 2 WARD SALESMAN 1250 2 MILLER CLERK 1300 2 ALLEN SALESMAN 1600 3 TURNER SALESMAN 1500 3 BLAKE MANAGER 2850 4 CLARK MANAGER 2450 4 JONES MANAGER 2975 4 FORD ANALYST 3000 4 SCOTT ANALYST 3000 4 KING PRESIDENT 5000 5

4. HiÓn thÞ tªn nh©n viªn, nghÒ nghiÖp, l−¬ng vµ møc l−¬ng, víi ®iÒu kiÖn møc l−¬ng = 3.

ENAME JOB SAL GRADE ---------- --------- ---------- ---------- ALLEN SALESMAN 1600 3 TURNER SALESMAN 1500 3

5. HiÓn thÞ nh÷ng nh©n viªn t¹i DALLAS

ENAME LOC SAL ---------- ------------- ---------- JONES DALLAS 2975 FORD DALLAS 3000 SMITH DALLAS 800 SCOTT DALLAS 3000 ADAMS DALLAS 1100

6. HiÓn thÞ tªn nh©n viªn , nghÒ nghiÖp, l−¬ng, møc l−¬ng, tªn phßng lµm viÖc trõ nh©n viªn cã nghÒ lµ cleck vµ s¾p xÕp theo chiÒu gi¶m.

ENAME JOB SAL GRADE DNAME ---------- --------- ---------- ---------- -------------- MARTIN SALESMAN 1250 2 SALES WARD SALESMAN 1250 2 SALES ALLEN SALESMAN 1600 3 SALES TURNER SALESMAN 1500 3 SALES




BLAKE MANAGER 2850 4 SALES CLARK MANAGER 2450 4 ACCOUNTING JONES MANAGER 2975 4 RESEARCH FORD ANALYST 3000 4 RESEARCH SCOTT ANALYST 3000 4 RESEARCH KING PRESIDENT 5000 5 ACCOUNTING

7. HiÓn thÞ chi tiÕt vÒ nh÷ng nh©n viªn kiÕm ®−îc 36000 $ 1 n¨m hoÆc nghÒ lµ cleck. (gåm c¸c tr−êng tªn, nghÒ, thu nhËp, m· phßng, tªn phßng, møc l−¬ng)

ENAME JOB ANUAL_SAL DNAME GRADE ---------- --------- ---------- -------------- ---------- JAMES CLERK 11400 SALES 1 SMITH CLERK 9600 RESEARCH 1 ADAMS CLERK 13200 RESEARCH 1 MILLER CLERK 15600 ACCOUNTING 2 FORD ANALYST 36000 RESEARCH 4 SCOTT ANALYST 36000 RESEARCH 4

8. HiÓn thÞ nh÷ng phßng kh«ng cã nh©n viªn nµo lµm viÖc.

DEPTNO DNAME LOC ---------- -------------- ------------- 40 OPERATIONS BOSTON

9. HiÓn thÞ m· nh©n viªn, tªn nh©n viªn, m· ng−êi qu¶n lý, tªn ng−êi qu¶n lý

EMP_NAME EMP_SAL MGR_NAME MGR_SAL ---------- ---------- ---------- ---------- BLAKE 2850 KING 5000 CLARK 2450 KING 5000 JONES 2975 KING 5000 MARTIN 1250 BLAKE 2850 ALLEN 1600 BLAKE 2850 TURNER 1500 BLAKE 2850 JAMES 950 BLAKE 2850 WARD 1250 BLAKE 2850 FORD 3000 JONES 2975 SMITH 800 FORD 3000 SCOTT 3000 JONES 2975 ADAMS 1100 SCOTT 3000 MILLER 1300 CLARK 2450

10. Nh− c©u 9 hiÓn thÞ thªm th«ng tin vÒ «ng KING.

EMP_NAME EMP_SAL MGR_NAME MGR_SAL ---------- ---------- ---------- ---------- KING 5000 BLAKE 2850 KING 5000 CLARK 2450 KING 5000 JONES 2975 KING 5000 MARTIN 1250 BLAKE 2850 ALLEN 1600 BLAKE 2850 TURNER 1500 BLAKE 2850 JAMES 950 BLAKE 2850 WARD 1250 BLAKE 2850 FORD 3000 JONES 2975 SMITH 800 FORD 3000 SCOTT 3000 JONES 2975 ADAMS 1100 SCOTT 3000 MILLER 1300 CLARK 2450

EMP_NAME EMP_SAL MGR_NAME MGR_SAL




---------- ---------- ---------- ---------- BLAKE 2850 BLAKE 2850 MARTIN 1250 BLAKE 2850 ALLEN 1600 BLAKE 2850 TURNER 1500 BLAKE 2850 JAMES 950 BLAKE 2850 WARD 1250 BLAKE 2850 CLARK 2450 CLARK 2450 MILLER 1300 CLARK 2450 JONES 2975 JONES 2975 FORD 3000 JONES 2975 SMITH 800 JONES 2975 SCOTT 3000 JONES 2975 ADAMS 1100 JONES 2975 13 rows selected.

11. HiÓn thÞ nghÒ nghiÖp ®−îc tuyÓn dông vµo n¨m 1981 vµ kh«ng ®−îc tuyÓn dông vµo n¨m 1994.

12. T×m nh÷ng nh©n viªn gia nhËp c«ng ty tr−íc gi¸m ®èc cña hä.

8 C¸c lÖnh truy vÊn lång nhau

8.1 C©u lÖnh SELECT lång nhau.

Trong mÖnh ®Ò WHERE

/T×m nh÷ng nh©n viªn lµm cïng nghÒ víi BLAKE/ select ename, job from emp where job = (select job from emp where ename = ‘BLAKE’); ENAME JOB ---------- -------- BLAKE MANAGER CLARK MANAGER JONES MANAGER

Trong mÖnh ®Ò HAVING

/T×m nh÷ng phßng cã møc l−¬ng trung b×nh lín h¬n phßng 30/ SELECT DEPTNO, AVG(SAL) FROM EMP HAVING AVG(SAL) > (SELECT AVG(SAL) FROM EMP WHERE DEPTNO =30) GROUP BY DEPTNO; DEPTNO AVG(SAL) --------- ---------- 10 2916.66667 20 2175

To¸n tö SOME/ANY/ALL/NOT IN/EXITS

NOT IN : Kh«ng thuéc

ANY vµ SOME : So s¸nh mét gi¸ trÞ víi mçi gi¸ trÞ trong mét danh s¸ch hay trong kÕt qu¶ tr¶ vÒ cña c©u hái con, ph¶i sau to¸n tö =

ALL : So s¸nh mét gi¸ trÞ víi mäi gi¸ trÞ trong danh s¸ch hay trong kÕt qu¶ tr¶ vÒ cña c©u hái con.

EXISTS : Tr¶ vÒ TRUE nÕu cã tån t¹i.

VÝ dô




SELECT * FROM emp WHERE sal = ANY (SELECT sal FROM emp WHERE deptno=30);

SELECT * FROM emp WHERE sal >= ALL ( select distinct sal From emp Where deptno =30)

Order by sal desc;

SELECT ENAME, SAL, JOB, DEPTNO

FROM EMP

WHERE SAL > SOME ( SELECT DISTINCT SAL

FROM EMP

WHERE DEPTNO =30)

ORDER BY SAL DESC;

SELECT EMPNO, ENAME, JOB, DEPTNO

FROM EMP E

WHERE EXISTS ( SELECT EMPNO

FROM EMP

WHERE EMP.MGR = E.EMPNO);

/T×m nh÷ng ng−êi cã nh©n viªn/

8.2 Bµi tËp

9 CÊu tróc h×nh c©y

9.1 CÊu tróc h×nh c©y trong 1 table

Trong mét table cña CSDL ORACLE cã thÓ hiÖn cÊu tróc h×nh c©y. VÝ dô trong b¶ng EMP cÊu tróc thÓ hiÖn cÊp ®é qu¶n lý.

KING EMPNO = 7839

CLARK JONES BLAKE

Mgr =7839

MILER SCOTT FORD ALLEN WARD MARTIN TUNNER JAMES

ADAMS SMITH

KING EMPNO = 7839

CLARK JONES BLAKE

Mgr =7839

MILER SCOTT FORD ALLEN WARD MARTIN TUNNER JAMES

ADAMS SMITH




• Root node lµ node cÊp cao nhÊt

• Child node lµ node con hay kh«ng ph¶i lµ root node

• Parent node lµ node cã node con

• Leaf node lµ node kh«ng cã node con

Level

Level lµ mét cét gi¶ chøa cÊp ®é trong cÊu tróc h×nh c©y. VÝ dô.

SELECT LEVEL, DEPTNO, EMPNO, ENAME, JOB, SAL FROM EMP CONNECT BY PRIOR EMPNO = MGR START WITH MGR is NULL; LEVEL DEPTNO EMPNO ENAME JOB SAL ---------- ---------- ---------- ---------- --------- ---------- 1 10 7839 KING PRESIDENT 5000 2 30 7698 BLAKE MANAGER 2850 3 30 7654 MARTIN SALESMAN 1250 3 30 7499 ALLEN SALESMAN 1600 3 30 7844 TURNER SALESMAN 1500 3 30 7900 JAMES CLERK 950 3 30 7521 WARD SALESMAN 1250 2 10 7782 CLARK MANAGER 2450 3 10 7934 MILLER CLERK 1300 2 20 7566 JONES MANAGER 2975 3 20 7902 FORD ANALYST 3000 4 20 7369 SMITH CLERK 800 3 20 7788 SCOTT SALEMAN 3300 4 20 7876 ADAMS CLERK 1100

9.2 Kü thuËt thùc hiÖn

Cã thÓ ®Þnh nghÜa quan hÖ thõa kÕ trong c©u hái b»ng mÖnh ®Ò STAR WITH vµ CONNECT BY trong c©u lªnh SELECT, mçi mÇu tin lµ mét node trong c©y ph©n cÊp. Cét gi¶ LEVEL cho biÕt cÊp cña mÉu tin hay cÊp cña node trong quan hÖ thõa kÕ.

Có ph¸p:

SELECT [DISTINCT/ALL] [expr [c_ias]] FROM [table/view/snapshot] [t_alias] [WHERE condition] [START WITH condition CONNECT BY PRIOR condition][START WITH condition CONNECT BY PRIOR condition][START WITH condition CONNECT BY PRIOR condition][START WITH condition CONNECT BY PRIOR condition] [GROUP BY expr] [HAVING condition] [UNION/UNION ALL/INTERSET/MINUS select command] [ORDER BY expr/position [DESC/ASC]]

Trong ®ã:

• START WITH §Æc t¶ ®iÓm ®Çu cña h×nh c©y. Kh«ng thÓ ®Ó column gi¶ level ë mÖnh ®Ó nµy.

• CONNECT BY ChØ column trong mèi liªn hÖ t×nh c©y.

• PRIOR §Þnh h−íng cÊu tróc. NÕu prior xuÊt hiÖn tr−íc mgr, Mgr sÏ ®−îc t×m tr−íc sau ®ã ®Õn empno, ®©y lµ h×nh c©y h−íng lªn. NÕu prior xuÊt hiÖn tr−íc empno, empno sÏ ®−îc t×m tr−íc sau ®ã ®Õn empno, ®©y lµ h×nh c©y h−íng xuèng.

VÝ dô

SELECT LEVEL, DEPTNO, EMPNO, ENAME, JOB, SAL FROM EMP CONNECT BY PRIOR MGR = EMPNOCONNECT BY PRIOR MGR = EMPNOCONNECT BY PRIOR MGR = EMPNOCONNECT BY PRIOR MGR = EMPNO START WITH empno = 7876;




LEVEL DEPTNO EMPNO ENAME JOB SAL ---------- ---------- ---------- ---------- --------- ---------- 1 20 7876 ADAMS CLERK 1100 2 20 7788 SCOTT SALEMAN 3300 3 20 7566 JONES MANAGER 2975 4 10 7839 KING PRESIDENT 5000

MÖnh ®Ò WHERE trong cÊu tróc h×nh c©y:

MÖnh ®Ò WHERE vµ CONNECT BY cã thÓ ®−îc dïng ®ång thêi trong cÊu tróc h×nh c©y. NÕu mÖnh ®Ò WHERE lo¹i trõ mét sè row cña cÊu tróc h×nh c©y th× chØ nh÷ng row ®ã ®−îc lo¹i trõ. NÕu ®iÒu kiÖn ®Æt trong mÖnh ®Ò CONNECT BY th× toµn bé nh¸nh cña row ®ã bÞ lo¹i trõ. V× dô

1. SELECT LEVEL, DEPTNO, EMPNO, ENAME, JOB, SAL FROM EMP WHERE ENAME != ‘SCOTT’ CONNECT BY PRIOR EMPNO = MGR START WITH MGR IS NULL; LEVEL DEPTNO EMPNO ENAME JOB SAL ---------- ---------- ---------- ---------- --------- ---------- 1 10 7839 KING PRESIDENT 5000 2 30 7698 BLAKE MANAGER 2850 3 30 7654 MARTIN SALESMAN 1250 3 30 7499 ALLEN SALESMAN 1600 3 30 7844 TURNER SALESMAN 1500 3 30 7900 JAMES CLERK 950 3 30 7521 WARD SALESMAN 1250 2 10 7782 CLARK MANAGER 2450 3 10 7934 MILLER CLERK 1300 2 20 7566 JONES MANAGER 2975 3 20 7902 FORD ANALYST 3000 4 20 7369 SMITH CLERK 800 4 20 7876 ADAMS CLERK 1100 2. SELECT LEVEL, DEPTNO, EMPNO, ENAME, JOB, SAL FROM EMP CONNECT BY PRIOR EMPNO = MGR AND ENAME != ‘SCOTT’ START WITH MGR IS NULL; LEVEL DEPTNO EMPNO ENAME JOB SAL ---------- ---------- ---------- ---------- --------- ---------- 1 10 7839 KING PRESIDENT 5000 2 30 7698 BLAKE MANAGER 2850 3 30 7654 MARTIN SALESMAN 1250 3 30 7499 ALLEN SALESMAN 1600 3 30 7844 TURNER SALESMAN 1500 3 30 7900 JAMES CLERK 950 3 30 7521 WARD SALESMAN 1250 2 10 7782 CLARK MANAGER 2450 3 10 7934 MILLER CLERK 1300 2 20 7566 JONES MANAGER 2975 3 20 7902 FORD ANALYST 3000 4 20 7369 SMITH CLERK 800

9.3 Bµi tËp

1. T×m tÊt c¶ c¸c nh©n viªn, ngµy gia nhËp c«ng ty, tªn nh©n viªn, tªn ng−êi gi¸m ®èc vµ ngµy gia nhËp c«ng ty cña ng−êi gi¸m ®èc Êy.

EMP_NAME EMP_SAL MGR_NAME MGR_SAL ---------- ---------- ---------- ---------- BLAKE 2850 BLAKE 2850 MARTIN 1250 BLAKE 2850 ALLEN 1600 BLAKE 2850 TURNER 1500 BLAKE 2850 JAMES 950 BLAKE 2850




WARD 1250 BLAKE 2850 CLARK 2450 CLARK 2450 MILLER 1300 CLARK 2450 JONES 2975 JONES 2975 FORD 3000 JONES 2975 SMITH 800 JONES 2975 SCOTT 3300 JONES 2975 ADAMS 1100 JONES 2975 13 rows selected.

2. T×m nh÷ng nh©n viªn kiÕm ®−îc l−¬ng cao nhÊt trong mçi lo¹i nghÒ nghiÖp.

JOB MAX(SAL) --------- --------- ANALYST 3000 CLERK 1300 MANAGER 2975 PRESIDENT 5000 SALESMAN 1600

3. T×m møc l−¬ng cao nhÊt trong mçi phßng ban, s¾p xÕp theo thø tù phßng ban.

ENAME JOB DEPTNO SAL ---------- --------- ---------- ---------- KING PRESIDENT 10 5000 SCOTT SALEMAN 20 3300 BLAKE MANAGER 30 2850

4. T×m nh©n viªn gia nhËp vµo phßng ban sím nhÊt

ENAME HIREDATE DEPTNO ---------- ---------- ---------- CLARK 09-06-1981 10 SMITH 17-12-1980 20 ALLEN 20-02-1981 30

5. HiÓn thÞ nh÷ng nh©n viªn cã møc l−¬ng lín h¬n l−¬ng TB cña phßng ban mµ hä lµm viÖc.

EMPNO ENAME SAL DEPTNO ---------- ---------- ---------- ---------- 7839 KING 5000 10 7566 JONES 2975 20 7902 FORD 3000 20 7788 SCOTT 3300 20 7698 BLAKE 2850 30 7499 ALLEN 1600 30

6. HiÓn thÞ tªn nh©n viªn, m· nh©n viªn, m· gi¸m ®èc, tªn gi¸m ®èc, phßng ban lµm viÖc cña gi¸m ®èc, møc l−¬ng cña gi¸m ®èc.

EMP_NUMBER EMP_NAME EMP_SAL MGR_NUMBER MGR_NAME MGR_DEPT MGR_GRADE ---------- --------------- ---------- ---------- ---------- ---------- 7698 BLAKE 2850 7698 BLAKE 30 4 7654 MARTIN 1250 7698 BLAKE 30 4 7499 ALLEN 1600 7698 BLAKE 30 4 7844 TURNER 1500 7698 BLAKE 30 4 7900 JAMES 950 7698 BLAKE 30 4 7521 WARD 1250 7698 BLAKE 30 4 7782 CLARK 2450 7782 CLARK 10 4 7934 MILLER 1300 7782 CLARK 10 4 7566 JONES 2975 7566 JONES 20 4 7902 FORD 3000 7566 JONES 20 4 7369 SMITH 800 7566 JONES 20 4 7788 SCOTT 3300 7566 JONES 20 4 7876 ADAMS 1100 7566 JONES 20 4 13 rows selected.




10 Tæng kÕt vÒ lÖnh select

CÊu tróc lÖnh

SELECT [DISTINCT/ALL] [expr [c_ias]] FROM [table/view/snapshot] [t_alias] [WHERE condition] [START WITH condition CONNECT BY condition] [GROUP BY expr] [HAVING condition] [UNION/UNION ALL/INTERSET/MINUS select command] [ORDER BY expr/position [DESC/ASC]] [FOR UPDATE OF [column]] [NOTWAIT]

Çc thµnh phÇn trong c©u lÖnh SELECT

DISTINCT ChØ chän 1 cho çc row gièng nhau trong kÕt qu¶ ALL KÕt xuÊt c¶ çc row gièng nhau * Chän tÊt c¶ çc column trong table, view... table.*,

view.*, snapshot.* Chän tÊt c¶ çc cét trong table, view hay snapshot ®−îc

chÞ ®Þnh expr Chän çc biÓu thøc c_alias Tªn cét trong kÕt qu¶ kÕt xuÊt. table, view, snapshot lµ

Tªn table, view hay snapshot subquery C©u hái select con t_alias Tªn cho çc table WHERE Chän çc row tháa ®iÒu kiÖn trong mÖnh ®Ò WHERE START WITH,CONNECT BY Chän çc dßng trong thø tù thõa kÕ GROUP BY Nhãm çc dßng cã expr gièng nhau HAVING Chän nh÷ng nhãm tháa ®iÒu kiÖn mÖnh ®Ò HAVING UNION, UNION ALL, INTERSET, MINUS Cho kÕt qu¶ kÕt hîp çc to¸n tö tËp

hîp ORDER BY XÕp thø t− çc row theo expr hay position (trong danh

s¸ch select) ASC, DESC TrËt tù xu«i (mÆc nhiªn) hay ng−îc FOR UPDATE Khãa nh÷ng row ®−îc chän, cho biÕt b¹n cã ý ®Þnh xãa hay

cËp nhËt çc row nµy NOTWAIT Tr¶ quyÒn ®iÒu khiÓn nÕu khi muèn lock row ®· bÞ lock

bëi user kh¸c.

11 T¹o table

11.1 LÖnh t¹o b¶ng

§Ó t¹o mét b¶ng míi dïng lÖnh CREATE TABLE, Có ph¸p nh− sau:

CREATE TABLE tablename (column [datatype][DEFAULT expr][column_constraint]..) [table_constraint]) [PCTFREE integer][PCTUSED integer] [INITRANS integer][MAXTRANS integer] [TABLESPACE tablespace] [STORAGE storage_clause] [AS subquery]

Trong ®ã:

tablename : Tªn table cÇn t¹o column : Tªn column trong table [datatype] : KiÓu d÷ liÖu cña column [DEFAULT expr] : Gi¸ trÞ mÆc ®Þnh cña column trong tr−êng hîp

NULL lµ expr [column_constraint] : Rµng buéc cña b¶n th©n column [table_constraint] : rµng buéc cña toµn b¶ng [PCTFREE integer] : % trèng [PCTUSED integer] : % sö dông [INITRANS integer] : Sè b¶n ghi khëi t¹o [MAXTRANS integer] : Sè b¶n ghi lín nhÊt




[TABLESPACE tablespace] : ChØ ®Þnh TABLESAPCE cho b¶ng [STORAGE storage_clause] : Ghi mÖnh ®Ò l−u tr÷, ®¬n vÞ mÆc ®Þnh lµ KB trong

®ã çc çc chän lùa lµ: INITIAL - dung l−îng khëi t¹o; NEXT - dung l−îng t¨ng tiÕp theo; MINEXTENTS - % më réng nhá nhÊt; MAXEXTENTS- % më réng lín nhÊt; PCTINCREASE - Tèc ®é t¨ng hµng n¨m.

[AS subquery] : t¹o b¶ng cã cÊu tróc gièng mÖnh ®Ò truy vÊn

VÝ dô 1

CREATE TABLE EMP (EMPNO NUMBER NOT NULL CONSTRAINT PK_EMP PRIMARY KEY, ENAME VARCHAR2(10) CONSTRAINT NN_ENAME NOT NULL CONSTRAINT UPPER_ENAME CHECK (ENAME = UPPER(ENAME)), JOB VARCHAR2(9), MGR NUMBER CONSTRAINT FK_MGR REFERENCES SCOTT.EMP(EMPNO), HIREDATE DATE DEFAULT SYSDATE, SAL NUMBER(10,2) CONSTRAINT CK_SAL CHECK(SAL>500), COMM NUMBER(9,0) DEFAULT NULL, DEPTNO NUMBER(2) CONSTRAINT NN_DEPTNO NOT NULL CONSTRAINT FK_DEPTNO REFERENCES SCOTT.DEPT(DEPTNO)) PCTFREE 5 PCTUSED 75

VÝ du 2

CREATE TABLE SALGRADE1 (GRADE NUMBER CONSTRAINT PK_SALGRADE PRIMARY KEY, LOSAL NUMBER, HISAL NUMBER) TABLESPACE USER STORAGE (INITIAL 6144 NEXT 6144 MINEXTENTS 1 MAXEXTENTS 5 PCTINCREASE 5)

VÝ dô 3

CREATE TABLE DEPT10 AS SELECT EMPNO, ENAME, JOB, SAL FROM EMP WHERE DEPTNO =10;

VÝ dô 4

CREATE TABLE EMP_SAL (NAME, SALARY,GRADE) AS SELECT ENAME, SAL, GRADE FROM EMP, SALGARDE WHERE EMP.SAL BETWEEN LOSAL AND HISAL ;

§Ó t¹o mét table míi, chóng ta cÇn ph¶i chuÈn bÞ mét sè th«ng tin sau:

• Table ph¶i ®−îc chuÈn hãa.

• Nh÷ng column mµ cho phÐp null nªn ®Þnh nghÜa sau ®Ó tiÕt kiÖm n¬i l−u tr÷.

• Gép çc table l¹i nÕu cã thÓ.

• ChØ ®Þnh çc th«ng sè pcfree vµ pctused

• Cã thÓ chØ ®Þnh 2 th«ng sè initstran, maxtrans

• Cã thÓ chØ ®Þnh tablespace cho table

• Cã thÓ −íc l−îng kÝch th−íc table, vµ çc th«ng sè cho storage.

TÝnh to¸n kÝch th−íc table (tham kh¶o):




1. TÝnh to¸n kho¶ng ®Üa cÇn thiÕt cho data block header. TÝnh theo c«ng thøc sau:

BLOCK HEADER = (FIXED HEADER + VARIABLE TRANSACTION HEADER) + ( TABLE DIRECTORY + ROW DIRECTORY) Trong ®ã: fixed header = 57 bytes variable transaction header = 23*gi¸ trÞ cña th«ng sè instrans table directory =4 row directory = 2* sè l−îng row trong block.

2. TÝnh to¸n kho¶ng ®Üa trèng ®Ó chøa d÷ liÖu cña data block. TÝnh theo c«ng thøc sau:

Kho¶ng ®Üa trèng ®Ó chøa data = (block size -total block header) - (block size -(fixed header+ variable transaction header))*(pctree/100) Cã thÓ biÕt block size b»ng çch dïng lÖnh show parameters db_block_size.

3. TÝnh to¸n kho¶ng ®Üa trèng kÕt hîp b»ng gi¸ trÞ cña mçi row.

4. TÝnh to¸n kÝch th−íc trung b×nh cña row:

KÝch th−íc trung b×nh cña row = row header +A+B+C A = Tæng chiÒu dµi cña çc cét <= 250 byte B = Tæng chiÒu dµi cña çc cét > 250 byte C = Kho¶ng ®Üa trèng kÕt hîp

5. QuyÕt ®Þnh sè row trung b×nh cho mét block:

avg rows /block = available space/average row size

6. TÝnh to¸n sè l−îng block

Block = sè row / sè row trung b×nh cho mét block

11.2 Çc quy t¾c ®Æt tªn object

• Tªn dµi tõ 1 ®Õn 30 ký tù, ngo¹i trõ tªn CSDL kh«ng qu¸ 8 ký tù vµ tªn liªn kÕt cã thÓ dµi ®Õn 128 ký tù

• Tªn kh«ng chøa dÊu nh¸y (")

• Kh«ng ph©n biÖt ch÷ hoa ch÷ th−êng

• Tªn ph¶i b¾t ®Çu b»ng ký tù ch÷ trong bé ký tù cña CSDL

• Tªn chØ cã thÓ chøa ký tù sè trong tËp ký tù cña CSDL. Cã thÓ dïng çc ký tù _, $, #. ORACLE kh«ng khuyÕn khÝch dïng çc ký tù $ vµ #.

• Tªn kh«ng ®−îc trïng víi çc tõ ®· dïng bëi ORACLE (xemphu lôc 1)

• Tªn kh«ng ®−îc çch kho¶ng trèng

• Tªn cã thÓ ®Æt trong cÆp dÊu nh¸y kÐp, khi ®ã tªn cã thÓ bao gåm çc ký tù bÊt kú, cã thÓ bao gåm kho¶ng trèng, cã thÓ dïng çc tõ khãa cña ORACLE, ph©n biÖt ch÷ hoa ch÷ th−êng.

• Tªn ph¶i duy nhÊt trong "kh«ng gian tªn" nhÊt ®Þnh. Çc object thuéc cïng kh«ng gian tªn ph¶i cã tªn kh¸c nhau.

Çc bÝ danh cña cét, bÝ danh b¶ng, tªn ng−êi sö dông, mËt khÈu mÆc dï kh«ng ph¶i lµ çc object hoÆc çc thµnh phÇn con cña object nh−ng còng ph¶i ®−îc ®Æt tªn theo çc quy t¾c trªn, ngo¹i trõ

BÝ danh cét, bÝ danh b¶ng chØ tån t¹i khi thùc hiÖn çc lÖnh SQL vµ kh«ng ®−îc l−u tr÷ trong CSDL, do vËy kh«ng ¸p dông quy t¾c 9 vÒ kh«ng gian tªn.

MËt khÈu kh«ng thuéc vÒ kh«ng gian tªn nµo vµ do ®ã còng kh«ng ¸p dông quy t¾c 9.

Nªn ®Æt tªn theo mét quy t¾c ®Æt tªn thèng nhÊt




11.3 Çc quy t¾c khi tham chiÕu ®Õn object

Có ph¸p chung khi tham chiÕu ®Õn çc object

S¬ ®å chung khi tham chiÕu çc object hoÆc thµnh phÇn cña çc object

Schema.Object.Part.@dblink

Trong ®ã

object Tªn object

schema Schema chøa object

part Thµnh phÇn cña object

dblink Tªn CSDL chøa object

ORACLE gi¶i quyÕt viÖc tham chiÕu çc object

Khi tham chiÕu ®Õn mét object trong c©u lÖnh SQL, ORACLE ph©n tÝch c©u lÖnh vµ vµ x¸c ®Þnh çc object trong kh«ng gian tªn. Sau khi x¸c ®Þnh çc object, ORACLE thùc hiÖn çc thao t¸c mµ c©u lÖnh quy ®Þnh trªn object. NÕu tªn object truy cËp kh«ng thuéc kh«ng gian tªn th× c©u lÖnh kh«ng ®−îc thùc hiÖn vµ cã th«ng b¸o lçi.

C©u lÖnh sau thªm mét mÈu tin vµo b¶ng DEPT

INSERT INTO Dept VALUES (50, 'SUPPOR', 'PARIS')

Theo ng÷ c¶nh cña c©u lÖnh, ORACLE x¸c ®Þnh b¶ng Dept cã thÓ lµ

• Mét table trong schema cña b¹n

• Mét view trong schema cña b¹n

• §ång nghÜa riªng cho table hoÆc view

• §ång nghÜa chung cho table hoÆc view

Tham chiÕu ®Õn çc object kh«ng thuéc quyÒn së h÷u

§Ó tham chiÕu ®Õn çc object kh«ng thuéc schema hiÖn thêi, ph¶i chØ ra tªn cña schema chøa object muèn truy cËp

schema.object

VÝ dô ®Ó xãa table EMP trong schema SCOTT

DROP TABLE scott.emp

Tham chiÕu çc object tõ xa

§Ó truy cËp ®Õn mét CSDL ë xa, sau tªn object ph¶i chØ ra tªn liªn kÕt CSDL (database link) cña CSDL chøa object muèn truy cËp. Database link lµ mét schema object, ORACLE dïng ®Ó th©m nhËp vµ truy xuÊt CSDL tõ xa.

11.4 KiÓu d÷ liÖu vµ ®iÒu kiÖn

11.4.1 CHAR

KiÓu CHAR dïng ®Ó khai b¸o mét chuçi cã chiÒu dµi cè ®Þnh, khi khai b¸o biÕn hoÆc cét kiÓu CHAR víi chiÒu dµi chØ ®Þnh th× tÊt c¶ çc môc tin cña biÕn hay cét nµy ®Òu cã cïng chiÒu dµi ®−îc chØ ®Þnh. Çc môc tin ng¾n h¬n ORACLE sÏ tù ®éng thªm vµo çc kho¶ng trèng cho ®ñ chiÒu dµi. ORACLE kh«ng cho phÐp




g¸n môc tin dµi h¬n chiÒu dµi chØ ®Þnh ®èi víi kiÓu CHAR. ChiÒu dµi tèi ®a cho phÐp cña kiÓu CHAR lµ 255 byte

11.4.2 VARCHAR2

KiÓu VARCHAR2 dïng ®Ó khai b¸o chuçi ký tù víi chiÒu dµi thay ®æi. Khi khai b¸o mét biÕn hoÆc cét kiÓu VARCHAR2 ph¶i chØ ra chiÒu dµi tèi ®a, çc môc tin chøa trong biÕn hay cét kiÓu VARCHAR2 cã chiÒu dµi thùc sù lµ chiÒu dµi cña môc tin. ORACLE kh«ng cho phÐp g¸n môc tin dµi h¬n chiÒu dµi tèi ®a chØ ®Þnh ®èi víi kiÓu VARCHAR2. ChiÒu dµi tèi ®a kiÓu VARCHAR2 lµ 2000 byte

11.4.3 VARCHAR

HiÖn t¹i ORACLE xem kiÓu VARCHAR2 vµ VARCHAR lµ nh− nhau, tuy nhiªn ORACLE khuyªn nªn dïng VARCHAR2. ORACLE dù ®Þnh trong t−¬ng lai dïng kiÓu VARCHAR ®Ó chøa çc chuçi víi chiÒu dµi biÕn ®æi, nh−ng trong phÐp so s¸nh sÏ ®−îc chØ ®Þnh theo nhiÒu ng÷ nghÜa kh¸c nhau.

11.4.4 NUMBER

KiÓu sè cña ORACLE dïng ®Ó chøa çc môc tin d¹ng sè d−¬ng, sè ©m, sè víi dÊu chÊm ®éng.

NUMBER(p, s) trong ®ã

p: sè ch÷ sè tr−íc dÊu chÊm thËp ph©n (precision), p tõ 1 ®Õn 38 ch÷ sè

s: sè çc ch÷ sè tÝnh tõ dÊu chÊm thËp ph©n vÒ bªn ph¶i (scale), s tõ -84 ®Õn 127

NUMBER(p) sè cã dÊu chÊm thËp ph©n cè ®Þnh víi precision b»ng p vµ scale b»ng 0

NUMBER sè víi dÊu chÊm ®éng víi precision b»ng 38. Nhí r»ng scale kh«ng ®−îc ¸p dông cho sè víi dÊu chÊm ®éng.

VÝ dô sau cho thÊy çch thøc ORACLE l−u tr÷ d÷ liÖu kiÓu sè tïy theo çch ®Þnh precision vµ scale kh¸c nhau

D÷ liÖu thùc KiÓu L−u tr÷

7456123.89 NUMBER 7456123.89

7456123.89 NUMBER(9) 7456123

7456123.89 NUMBER(9,2) 7456123.89

7456123.89 NUMBER(9,1) 7456123.8

7456123.89 NUMBER(6) Kh«ng hîp lÖ

7456123.8 NUMBER(15,1) 7456123.8

7456123.89 NUMBER(7,-2) 7456100

7456123.89 NUMBER(-7,2) Kh«ng hîp lÖ

11.4.5 FLOAT

Dïng ®Ó khai b¸o kiÓu sè dÊu chÊm ®éng, víi ®é chÝnh x¸c thËp ph©n 38 hay ®é chÝnh x¸c nhÞ ph©n lµ 126.

FLOAT(b) Khai b¸o kiÓu dÊu chÊm ®éng víi ®é chÝnh x¸c nhÞ ph©n lµ b, b tõ 1 ®Õn 126. Cã thÓ chuyÓn tõ ®é chÝnh x¸c nhÞ phËn sang ®é chÝnh x¸c thËp ph©n b»ng çch nh©n ®é chÝnh x¸c nhÞ ph©n víi 0.30103




11.4.6 LONG

Dïng ®Ó khai b¸o kiÓu chuçi ký tù víi ®é dµi biÕn ®æi, chiÒu dµi tèi ®a cña kiÓu LONG lµ 2 gigabyte. KiÓu LONG th−êng ®−îc dïng ®Ó chøa çc v¨n b¶n.

Cã mét sè h¹n chÕ khi dïng kiÓu LONG

• Mét table kh«ng thÓ chøa nhiÒu h¬n mét cét kiÓu LONG

• D÷ liÖu kiÓu LONG kh«ng thÓ tham gia vµo çc rµng buéc toµn vÑn, ngo¹i trõ kiÓm tra NULL vµ kh¸c NULL

• Kh«ng thÓ index mét cét kiÓu LONG

• Kh«ng thÓ truyÒn tham sè kiÓu LONG cho hµm hoÆc thñ tôc

• Çc hµm kh«ng thÓ tr¶ vÒ d÷ liÖu kiÓu LONG

• Trong c©u lÖnh SQL cã truy cËp çc cét kiÓu LONG, th× viÖc cËp nhËt hoÆc khãa çc b¶ng chØ cho phÐp trong cïng mét CSDL

Ngoµi ra, çc cét kiÓu LONG kh«ng ®−îc tham gia trong çc thµnh phÇn sau cña c©u lÖnh SQL

• Çc mÖnh ®Ò WHERE, GROUP BY, ORDER BY, CONNECT BY hoÆc víi t¸c tö DISTINCT trong c©u lÖnh SELECT

• Çc hµm sö dông trong c©u lÖnh SQL nh− SUBSTR, INSTR

• Trong danh s¸ch lùa chän cña c©u lÖnh SELECT cã sö dông mÖnh ®Ò GROUP BY

• Trong danh s¸ch lùa chän cña c©u hái con, c©u hái cã sö dông çc to¸n tö tËp hîp

• Trong danh s¸ch lùa chän cña c©u lÖnh CREATE TABLE AS SELECT

11.4.7 DATE

Dïng ®Ó chøa d÷ liÖu ngµy vµ thêi gian. MÆc dï kiÓu ngµy vµ thêi gian cã thÓ ®−îc chøa trong kiÓu CHAR vµ NUMBER.

Víi gi¸ trÞ kiÓu DATE, nh÷ng th«ng tin ®−îc l−u tr÷ gåm thÕ kû, n¨m, th¸ng, ngµy, giê, phót, gi©y. ORACLE kh«ng cho phÐp g¸n gi¸ trÞ kiÓu ngµy trùc tiÕp, ®Ó g¸n gi¸ trÞ kiÓu ngµy, b¹n ph¶i dïng TO_DATE ®Ó chuyÓn gi¸ trÞ kiÓu chuçi ký tù hoÆc kiÓu sè.

NÕu g¸n mét gi¸ trÞ kiÓu ngµy mµ kh«ng chØ thêi gian th× thêi gian mÆc ®Þnh lµ 12 giê ®ªm, NÕu g¸n gi¸ trÞ kiÓu ngµy mµ kh«ng chØ ra ngµy, th× ngµy mÆc ®Þnh lµ ngµy ®Çu cña th¸ng. Hµm SYSDATE cho biÕt ngµy vµ thêi gian hÖ thèng.

TÝnh to¸n ®èi víi kiÓu ngµy

§èi víi d÷ liÖu kiÓu ngµy, b¹n cã thÓ thùc hiÖn çc phÐp to¸n céng vµ trõ.

VÝ dô

SYSDATE+1 ngµy h«m sau

SYSDATE-7 çch ®©y mét tuÇn

SYSDATE+(10/1440) m−êi phót sau

Ngµy Julian: Lµ gi¸ trÞ sè cho biÕt sè ngµy kÓ tõ ngµy 1 th¸ng giªng n¨m 4712 tr−íc c«ng nguyªn.

VÝ dô




SELECT TO_CHAR (TO_DATE('01-01-1992', 'MM-DD-YYYY'), 'J') JULIAN FROM DUAL

Cho kÕt qu¶

JULIAN

-----------------------------------------------

2448623

11.4.8 RAW vµ LONG RAW

KiÓu RAW vµ LONG RAW dïng ®Ó chøa çc chuçi byte, çc d÷ liÖu nhÞ ph©n nh− h×nh ¶nh, ©m thanh. Çc d÷ liÖu kiÓu RAW chØ cã thÓ g¸n hoÆc truy cËp chø kh«ng ®−îc thùc hiÖn çc thao t¸c nh− ®èi víi chuçi ký tù.

KiÓu RAW gièng nh− kiÓu VARCHAR2 vµ kiÓu LONG RAW gièng kiÓu LONG, chØ kh¸c nhau ë chæ ORACLE tù ®éng chuyÓn ®æi çc gi¸ trÞ kiÓu CHAR, VARCHAR2 vµ LONG gi÷a tËp hîp ký tù cña CSDL vµ tËp ký tù cña çc øng dông.

11.4.9 ROWID

Mçi mÉu tin trong CSDL cã mét ®Þa chØ cã kiÓu ROWID. ROWID gåm

block.row.file, trong ®ã

block : chuçi hÖ hexa cho biÕt block chøa row

row : chuçi hÖ hexa cho biÕt row trong block

file : chuçi hÖ hexa cho biÕt database file chøa block

VÝ dô

0000000F.0000.0002

Row ®Çu tiªn trong block 15 cña data file thø hai.

11.4.10 MLSLABEL

KiÓu MLSLABEL dïng ®Ó chøa label d¹ng nhÞ ph©n mµ ORACLE dïng ®Ó ®¶m b¶o ho¹t ®éng cña b¶n th©n hÖ thèng.

11.4.11 ChuyÓn ®æi kiÓu

Nãi chung mét biÓu thøc kh«ng thÓ gåm çc gi¸ trÞ thuéc nhiÒu kiÓu kh¸c nhau, tuy nhiªn ORACLE cho phÐp chuyÓn ®æi gi−· çc kiÓu d÷ liÖu. ORACLE tù ®éng chuyÓn kiÓu cña d÷ liÖu trong mét sè tr−êng hîp sau

• Khi INSERT hoÆc UPDATE g¸n gi¸ trÞ cho cét cã kiÓu kh¸c, ORACLE sÏ tù ®éng chuyÓn gi¸ trÞ sang kiÓu cña cét.

• Khi sö dông çc hµm hoÆc çc to¸n tö mµ çc tham sè cã kiÓu kh«ng t−¬ng thÝch th× ORACLE sÏ tù ®éng chuyÓn kiÓu.

• Khi sö dông to¸n tö so s¸nh mµ çc gi¸ trÞ cã çc kiÓu kh¸c nhau, ORACLE sÏ tù ®éng chuyÓn kiÓu.

VÝ dô 1

SELECT ename FROM emp WHERE hiredate = '12-MAR-1993'

ORACLE ®· tù ®éng chuyÓn chuçi '12-MAR-1993' sang kiÓu DATE trong phÐp so s¸nh

VÝ dô 2

SELECT ename FROM emp WHERE ROWID = '00002514.0001.0001'




ORACLE ®· tù ®éng chuyÓn chuçi '00002514.0001.0001' sang kiÓu ROWID trong phÐp so s¸nh

Ng−êi sö dông tù chuyÓn ®æi

ORACLE cung cÊp çc hµm ®Ó chuyÓn ®æi kiÓu, vÝ dô

• TO_NUMBER ChuyÓn sang kiÓu sè

• TO_CHAR ChuyÓn sang kiÓu ký tù

• TO_DATE ChuyÓn sang kiÓu ngµy

(xem phÇn tra cøu çc hµm vµ thñ tôc)

11.5 Constraint

Çc d¹ng constraint gåm:

- NULL/NOT NULL - UNIQUE - PRIMARY KEY - FOREIGN KEY ( Referential ) - CHECK

NULL/NOT NULL: rµng buéc column trèng hoÆc kh«ng trèng, trong vÝ dô mÖnh ®Ò rµng buéc:

CREATE TABLE DEPT ( DEPTNO NUMBER(2) NOT NULL,NOT NULL,NOT NULL,NOT NULL, DNAME CHAR(14), LOC CHAR(13), CONSTRAINT DEPT_PRIMARY_KEY PRIMARY KEY (DEPTNO));

UNIQUE: ChØ ra rµng buéc duy nhÊt, çc gi¸ trÞ cña column chØ trong mÖnh ®Ò UNIQUE trong çc row cña table ph¶i cã gi¸ trÞ kh¸c biÖt. Gi¸ trÞ null lµ cho phÐp nªu UNIQUE dùa trªn mét cét. Vd:

CREATE TABLE DEPT ( DEPTNO NUMBER(2), DNAME CHAR(14), LOC CHAR(13), CONSTRAINT UNQ_DEPT_LOC UNIQUE(DNAME, LOC));

PRIMARY KEY: ChØ ra rµng buéc duy nhÊt (gièng UNIQUE), tuy nhiªn kho¸ lµ d¹ng kho¸ UNIQUE cÊp cao nhÊt. Mét table chØ cã thÓ cã mét PRIMARY KEY. Çc gi¸ trÞ trong PRIMARY KEY ph¶i NOTT NULL.

Có ph¸p khi ®Æt CONSTRAINT ë møc TABLE [CONSTRAINT constraint_name] PRIMARY KEY (column, Column..) Có ph¸p khi ®Æt CONSTRAINT ë møc COLUMN [CONSTRAINT constraint_name] PRIMARY KEY

FOREIGN KEY ( Referential ): ChØ ra mèi liªn hÖ rµng buéc tham chiÕu gi÷a table nµy víi table kh¸c, hoÆc trong chÝnh 1 table. Nã chØ ra mèi liªn hÖ cha-con vµ chØ rµng buéc gi÷a FOREIGN KEY b¶ng nµy víi PRIMARY KEY hoÆc UNIQUE Key cña b¶ng kh¸c. VÝ dô quan hÖ gi÷a DEPT vµ EMP th«ng qua tr−êng DEPTNO.

Tõ kho¸ ON DELETE CASCADE ®−îc hØ ®Þnh trong d¹ng kho¸ nµy ®Ó chØ khi d÷ liÖu cha bÞ xo¸ (trong b¶ng DEPT) th× d÷ liÖu con còng tù ®éng bÞ xo¸ theo (trong b¶ng EMP).

CHECK: Rµng buéc kiÓm tra gi¸ trÞ

VÝ dô: CREATE TABLE EMP (EMPNO NUMBER NOT NULL CONSTRAINT PK_EMP PRIMARY KEY, ENAME VARCHAR2(10) CONSTRAINT NN_ENAME NOT NULL CONSTRAINT UPPER_ENAME CHECK (ENAME = UPPER(ENAME)),




JOB VARCHAR2(9), MGR NUMBER CONSTRAINT FK_MGR REFERENCES SCOTT.EMP(EMPNO), HIREDATE DATE DEFAULT SYSDATE, SAL NUMBER(10,2) CONSTRAINT CK_SAL CHECK(SAL>500), COMM NUMBER(9,0) DEFAULT NULL, DEPTNO NUMBER(2) CONSTRAINT NN_DEPTNO NOT NULL CONSTRAINT FK_DEPTNO REFERENCES SCOTT.DEPT(DEPTNO);

11.6 Bµi tËp

1. T¹o b¶ng PROJECT víi çc column ®−îc chØ ra d−íi ®©y, PROJID lµ promary key, vµ P_END_DATE > P_START_DATE.

Column name Data Type Size. ------------------------------------ PROJID NUMBER 4 P_DESC VARCHAR2 20 P_START_DATE DATE P_END_DATE DATE BUDGET_AMOUNT NUMBER 7,2 MAX_NO_STAFF NUMBER 2

2.. T¹o b¶ng ASSIGNMENTS víi çc column ®−îc chØ ra d−íi ®©y, ®ång thêi cét PROJID lµ foreign key tíi b¶ng PROJECT, cét EMPNO lµ foreign key tíi b¶ng EMP.

Column name Data Type Size. ------------------------------------------------ PROJID NUMBER 4 NOT NULL EMPNO NUMBER 4 NOT NULL A_START_DATE DATE A_END_DATE DATE BILL_AMOUNT NUMBER 4,2 ASSIGN_TYPE VARCHAR2 2

12 çc lÖnh DDL kh¸c vµ d÷ liÖu trong tõ ®iÓn d÷ liÖu

12.1 ChØnh söa cÊu tróc table

Dïng lÖnh ALTER TABLE ®Ó chØnh söa cÊu tróc b¶ng. Có ph¸p nh− sau:

ALTER TABLE tablename [ADD/MODIFY/DROP options ([column [column constraint) [ENABLE clause] [DISABLE clause]

Trong ®ã:

ADD: thªm column hay constraint. MODIFY: söa ®æi kiÓu çc column DROP: bá constraint. ENABLE/DISABLE: Che khuÊt hoÆc ®−a vµo sö dông çc CONSTRAINT mµ kh«ng xãa h¼n

Chó ý:

• KhÝ dïng mÖnh ®Ò MODIFY kh«ng thÓ chuyÓn tÝnh chÊt cña COLUMN cã néi dung lµ NULL chuyÓn thµnh NOT NULL;

• Kh«ng thÓ ®−a thªm mét cét NOT NUL nÕu table ®· cã sè liÖu. Ph¶i thªm cét NULL, ®iÒn ®Çy sè liÖu, sau ®ã chuyÓn thµnh NOT NULL.

• Kh«ng thÓ chuyÓn ®æi kiÓu kh¸c nhau nÕu column ®· chøa sè liÖu

• Kh«ng thÓ dïng mÖnh ®Ò MODIFY ®Ó ®Þnh nghÜa çc CONSTRAINT trõ rµng buéc NULL/NOT NULL. Muèn söa CONSTRAINT cÇn xo¸ chóng sau ®ã ADD thªm vµo.




VÝ dô 1

ALTER TABLE emp ADD (spouse_name CHAR(10);

VÝ dô 2

ALTER TABLE emp MODIFY (ename CHAR(25);

VÝ dô 3

ALTER TABLE emp DROP CONSTRAINT emp_mgr; ALTER TABLE DROP PRIMARY KEY;

VÝ dô 4

ALTER TABLE dept DISABLE CONSTRAINT dept_prim;

12.2 Çc lÖnh DDL kh¸c

12.2.1 Xãa table

Dïng lÖnh DROP TABLE ®Ó xo¸ b¶ng. Có ph¸p nh− sau:

DROP TABLE table_name [CASCADE CONSTRAINTS]

Trong ®ã:

Option CASCADE ®Ó xãa tÊt c¶ çc rµng buéc toµn vÑn liªn quan ®Õn table bÞ xãa.

VÝ dô:

DROP TALE emp

Khi drop table th×:

• Xãa tÊt c¶ d÷ liÖu

• View vµ synonymliªn quan vÉn cßn nh−ng kh«ng cã gi¸ trÞ

• Çc giao dÞch ch−a gi¶i quyÕt xong sÏ ®−îc commit

• ChØ ng−êi t¹o ra table hay DBA míi cã thÓ xãa table

12.2.2 Gi¶i thÝch b¶ng

Dïng lÖnh COMMENT ®Ó chó thÝch. VÝ dô

COMMENT ON TABLE EMP IS ‘ THONG TIN NHAN VIEN’; COMMENT ON COLUMN EMP.EMPNO IS ‘ MA SO NHAN VIEN’;

12.2.3 Thay ®æi tªn object

Dïng lÖnh RENAME ®Ó thay ®æi tªn object. Có ph¸p nh− sau:

RENAME old TO new

Trong ®ã:

Old: Tªn cò New: tªn míi

VÝ dô

RENAME emp TO employee

12.2.4 Xãa d÷ liÖu cña table

Dïng lÖnh TRUNCATE TABLE ®Ó xãa d÷ liÖu cña table, xãa tÊt c¶ çc row trong table. Có ph¸p nh− sau:

TRUNCATE TABLE table_name [REUSE STORAGE]

Trong ®ã:




Option REUSE STORAGE gi÷ l¹i khung ®Ó chøa, chØ xãa d÷ liÖu

12.3 D÷ liÖu trong tõ ®iÓn d÷ liÖu

Trung t©m cña c¬ së d÷ liÖu ORACLE lµ data dictionary. Data dictionary tù ®éng ®−îc t¹o ra khi c¬ së d÷ liÖu ORACLE ®−îc t¹o. ORACLE cËp nhËt lªn data dictionary b»ng çc lÖnh DDL (Data Define Language). Çc table cña tõ ®iÓn d÷ liÖu ®−îc t¹o ra b»ng lÖnh CREATE DATABASE vµ chØ ®−îc t¹o tõ user SYS. Çc view trong tõ ®iÓn d÷ liÖu chøc çc th«ng tin d−íi d¹ng dÔ nh×n h¬n b¶ng.

Cã çc d¹ng view lµ:

• USER_xxx: lµ nh÷ng ®èi t−îng thuéc user , vÝ dô çc b¶ng ®−îc t¹o bëi user

• ALL_xxx: lµ tÊt c¶ çc ®èi t−îng mµ user cã quyÒn truy nhËp

• DBA_xxx: tÊt c¶ çc ®èi t−îng trong database

• V$: Çc thùc thi cña Server.

Ngoµi ra cßn cã çc view quan träng kh¸c lµ:

• DICTIONARY: Th«ng tin vÒ toµn bé çc table, view, snapshot trong tõ ®iÓn d÷ liÖu

• TABLE_PRIVILEGES: Th«ng tin vÒ viÖc g¸n quyÒn trªn çc ®èi t−îng

• IND: ®ång nghÜa cña USER_INDEX.

Muèn hiÓn thÞ toµn bé th«ng tin vÒ çc table, view, snapshot trong tõ ®iÓn d÷ liÖu dïng lÖnh

SELECT * FROM DICTIONARY;

HiÓn thÞ cÊu cña USER_OBJECT

DESCRIBE USER_OBJECT;

HiÓn thÞ tÊt c¶ çc b¶ng m· user ®ã së h÷u:

SELECT OBJECT_NAME FROM USER_OBJECT WHERE OBJECT_TYPE = ‘TABLE’; SELECT * FROM TAB; SELECT TABLE_NAME FROM USER_TABLE;

HiÓn thÞ tÊt c¶ çc lo¹i ®èi t−îng trong tõ ®iÓn d÷ liÖu:

SELECT DISTINCT OBJECT_TYPE FROM USER_OBJECTS;

12.4 Bµi tËp

1. Thªm column COMMENTS kiÓu LONG vµo b¶ng PROJECTS. Thªm column HOURS kiÓu NUMBER vµo b¶ng ASSIGNMENTS.

2. Sö dông view USER_OBJECTS hiÓn thÞ tÊt c¶ çc ®èi t−îng user së h÷u.

3. Thªm rµng buéc duy nhÊt (UNIQUE) cho 2 column PROJECT_ID vµ EMPNO cña b¶ng ASSIGNMENTS.

4. Xem çc th«ng tin vÒ çc rµng buéc trong USER_CONSTRAINTS.

5. Xem trong USER hiÖn t¹i cã tÊt c¶ bao nhiªu b¶ng.




13 Çc lÖnh Thao t¸c d÷ liÖu kh¸c

13.1 ChÌn mét row vµo table

§Ó chÌn mét row vµo table dïng lÖnh INSERT. Có ph¸p nh− sau:

INSERT INTO tablename ([column, column, ...]) VALUES (value, value ...);

VÝ dô

INSERT INTO dept (depno, dname, loc) VALUES (50, 'MARKETING', 'SAN JOSE')

ChÐp d÷ liÖu tõ table kh¸c

INSERT INTO table [(column, column...)] SELECT select_list FROM table(s)

VÝ dô

INSERT INTO emp_tmp (ename, sal) SELECT ename, sal FROM emp WHERE sal > 1000

13.2 ChØnh söa d÷ liÖu

§Ó chØnh söa d÷ liÖu dïng lÖnh UPDATE. Có ph¸p nh− sau :

UPDATE table [alias] SET column [,column...] = [expr, subquery] [WHERE condition]

VÝ dô 1

UPDATE emp SET job = 'SALEMAN', hiredate = sysdate, sal = sal * 1.1 WHERE ename = 'SCOTT';

VÝ dô 2

UPDATE emp SET comm = (SELECT comm FROM commission C WHERE C.empno = emp.empno) WHERE empno IN (SELECT empno FROM commission);

VÝ dô 3

UPDATE emp a SET deptno = (SELECT deptno FROM dept WHERE loc = 'BOSTON'), (sal, comm) = (SELECT 1.1*AVG(sal),1.5*AVG(comm) FROM emp b WHERE a.deptno = b.deptno) WHERE deptno IN (SELECT deptno FROM dept WHERE loc = 'DALLAS' OR loc = 'DETROIT'); Chó thÝch: - CËp nhËt çc nh©n viªn ë Dallas hoÆc Detroit - Thay DEPTNO cña çc nh©n viªn nµy b»ng DEPTNO cña Boston - Thay l−¬ng cña mçi nh©n viªn b»ng l−¬ng trung b×nh cña bé phËn * 1.1 - Thay commission cña mçi nh©n viªn b»ng commission trung b×nh cña bé phËn * 1.5

13.3 Xãa dßng

§Ó xãa dßng dïng lÖnh DELETE. Có ph¸p nh− sau:




DELETE FROM table [WHERE condition]

VÝ dô

DELETE FROM emp

WHERE deptno = 10;

13.4 Lçi rµng buéc d÷ liÖu

Th«ng th−êng khi thùc hiÖn çc lÖnh thao t¸c d÷ liÖu hay gÆp ph¶i çc lçi rµng buéc toµn vÑn d÷ liÖu. Çc lçi nµy xuÊt hiÖn khi cã çc rµng buéc tr−íc ®ã mµ d÷ liÖu nhËp vµo, chØnh söa hay khi xo¸ ®i kh«ng ®¶m b¶o çc ®iÒu kiÖn toµn vÑn. M· lçi:

ORA_02292: INTEGRITY CONSTRAINT Sau ®ã b¸o tªn cña Constraint bÞ lçi.

13.5 LÖnh ®iÒu khiÓn giao dÞch

Mét c©u lÖnh SQL cã thÓ gåm

• LÖnh DML thao t¸c d÷ liÖu

• LÖnh DDL ®Þnh nghÜa d÷ liÖu

• LÖnh DCL ®iÒu khiÓn truy nhËp d÷ liÖu

Mét giao dÞch b¾t ®Çu khi mét lÖnh SQL ®−îc thùc hiÖn

Mét giao dÞch kÕt thóc mét trong çc tr−êng hîp sau:

• COMMIT hoÆc ROLLBACK

• Çc lÖnh DDL vµ DCL thùc hiÖn (tù ®éng commit)

• Lçi, tho¸t khái SQL*Plus, hÖ thèng bÞ down.

Có ph¸p çc lÖnh ®iÒu khiÓn giao dÞch:

COMMIT KÕt thóc giao dÞch hiÖn t¹i, thùc hiÖn çc chuyÓn ®æi d÷ liÖu

SAVEPOINT name X¸c ®Þnh ®iÓm savepoint cña giao dÞch

ROLLBACK [TO SAVEPOINT name] Quay l¹i d÷ liÖu ë ®iÓm SAVEPOINT hoÆc toµn bé giao dÞch.

SET AUTO[COMMIT] ON/OFF Tù ®éng COMMIt khi thùc hiÖn çc lÖnh Insert, update, delete.

VÝ dô: INSERT INTO DEPT VALUES (50,’TESTING’,’LAS VEGAS’); SAVEPOINT INSERT_DONE; UPDATE DEPT SET DNAME = ‘MARKETING’; ROLLBACK TO INSERT_DONE ; UPDATE DEPT SET DNAME = ‘MARKETING’ WHERE DNAME =’SALES’; COMMIT;




13.6 Bµi tËp

1. Thªm d÷ liÖu vµo b¶ng PROJECTS.

PROJID 1 2 P_DESC WRITE C030 COURSE PROOF READ NOTES P_START_DATE 02-JAN-88 01-JAN-89 P_END_DATE 07-JAN-88 10-JAN-89 BUDGET_AMOUNT 500 600 MAX_NO_STAFF 1 1

2. Thªm d÷ liÖu vµo b¶ng ASSIGNMENTS.

PROJID 1 1 2 EMPNO 7369 7902 7844 A_START_DATE 01-JAN-88 04-JAN-88 01-JAN-89 A_END_DATE 03-JAN-88 07-JAN-88 10-JAN-89 BILL_RATE 50.00 55.00 45.50 ASSIGN_TYPE WR WR PF HOURS 15 20 30

3. CËp nhËt tr−êng ASIGNMENT_TYPE tõ WT thµnh WR.

4. NhËp thªm sè liÖu vµo b¶ng ASSIGNMENTS.

14 Sequence vµ index

14.1 Sequence

14.1.1 T¹o Sequence

Sequence lµ danh s¸ch tuÇn tù cña con sè, vµ ®−îc t¹o bëi Oracle sever. Sequence dïng ®Ó t¹o khãa chÝnh mét çch tù ®éng cho d÷ lÖu.

Sequence th−êng dïng ®Ó t¹o khãa chÝnh trong sinh m· tù ®éng. Cã thÓ dïng chung cho nhiÒu ®èi t−îng. Con sè sequence nµy cã chiÒu dµi tèi ®a lµ 38 sè.

§Ó t¹o sequence, dïng lÖnh create nh− sau

CREATE SEQUENCE sequence_name INCREMENT BY integer START WITH integer [MAXVALUE integer] [MINVALUE integer] [CYCLE/NO CYCLE]; Trong ®ã: INCREMENT BY : chØ ®Þnh kho¶ng çch cña d·y sè tuÇn tù START WITH : ChØ ®Þnh sè ®Çu tiªn cña d·y sè tuÇn tù MAXVALUE : Gi¸ trÞ lín nhÊt cña d·y tuÇn tù MINVALUE : Gi¸ trÞ nhá nhÊt cña d·y tuÇn tù CYCLE/NO CYCLE: D·y tuÇn tù cã quay vßng khi ®Õn ®iÓm cuèi. MÆc ®Þnh lµ NO

CYCLE

VÝ dô:

CREATE SEQUENCE sample_sequence INCREMENT 1 STRAT WITH 2 MAXVALUE 100;

§Ó lµm viÖc víi çc sequence, dïng lÖnh SQL víi çc cét gi¶ sau

CURRVAL Cho gi¸ tri hiÖn thêi cña sequence

NEXTVAL T¨ng gi¸ tri hiÖn thêi cña sequence vµ cho gi¸ trÞ sau khi t¨ng ph¶i x¸c ®Þnh tªn sequence tr−íc currval vµ nextval




sequence.CURRVAL

sequence.NEXTVAL

§Ó truy cËp çc sequence kh«ng thuéc schema hiÖn thêi, th× ph¶i chØ ra tªn schema

schema.sequence.CURRVAL

schema.sequence.NEXTVAL

§Ó truy cËp çc sequence tõ xa, th× cßn ph¶i chØ ra datalink

schema.sequence.CURRVAL@dblink

schema.sequence.NEXTVAL@dblink

Sö dông sequence

CURRVAL vµ NEXTVAL cã thÓ ®−îc sö dông trong çc tr−êng hîp sau:

• Trong danh s¸ch lùa chän cña c©u lÖnh SELECT

• Trong mÖnh ®Ò VALUES cña c©u lÖnh INSERT

• Trong mÖnh ®Ò SET cña c©u lÖnh UPDATE

• Kh«ng ®−îc sö dông CURRVAL vµ NEXTVAL trong çc tr−êng hîp sau

• Trong c©u hái con

• Trong çc view vµ snapshot

• Trong c©u lÖnh SELECT cã t¸c tö DISTINCT

• Trong c©u lÖnh SELECT cã sö dông GROUP BY hay ORDER BY

• Trong c©u lÖnh SELECT cã sö dông çc phÐp to¸n tËp hîp nh− UNION, INTERSET, MINUS

• Trong mÖnh ®Ò WHERE cña c©u lÖnh SELECT

• GÝa trÞ DEFAULT cña cét trong c©u lÖnh CREATE TABLE hay ALTER TABLE

• Trong ®iÒu kiÖn cña rµng buéc CHECK

14.1.2 Xo¸ vµ söa sequence

Söa b»ng lÖnh:

ALTER SEQUENCE sequence_name INCREMENT BY integer START WITH integer [MAXVALUE integer] [MINVALUE integer] [CYCLE/NO CYCLE];

Xo¸ b»ng lÖnh:

DROP SEQUENCE sequence_name ;

14.2 Index

Index lµ mét cÊu tróc c¬ së d÷ liÖu, ®−îc sever sö dông ®Ó t×m mét row trong b¶ng mét çch nhanh chãng. Index bao gåm mét key value ( mét cét (column) trong hµng (row) ) vµ rowid.

Có ph¸p:

CREATE [UNIQUE]] INDEX index_name ON TABLE ( column [,column...]);




• Dïng index ®Ó query cho nhanh.

• Dïng Index khi mµ viÖc lÊy d÷ liÖu <15% sè row trong b¶ng.

• Index nh÷ng column nµo dïng ®Ó nèi gi÷a çc b¶ng lÉn nhau.

• Kh«ng nªn dïng Index cho çc b¶ng nµo chØ cã vµi row.

• Primaryvµ unique key ( khãa chÝnh vµ khãa duy nhÊt) tù ®éng cã index, nh−ng nªn cã index cho foreign key( khãa ngo¹i).

Sè l−îng index cho mét table lµ kh«ng giíi h¹n. Tuy nhiªn nÕu cã qu¸ nhiÒu index sÏ g©y ¶nh h−ëng ®Õn sè liÖu khi mµ d÷ liÖu trong table bÞ thay ®æi thø tù theo index. VÝ dô: Thªm mét row vµo b¶ng tÊt c¶ çc Index sÏ ®−îc update. Nªn chän lùa gi÷a yªu cÇu query, vµ insert, update ®Ó cã mét index hîp lý. §èi víi çc kho¸ PRIMARY KEY vµ UNIQUE KEY tõ kho¸ UNIQUE ®−îc tù ®éng thªm khi t¹o INDEX.

VÝ dô:

CREATE INDEX i-ENAME ON EMP (ENAME);

Xo¸ INDEX b»ng lÖnh:

DROP INDEX index_name ;

14.3 Bµi tËp

1. T¹o Index trªn cét PROJID cho b¶ng ASSIGNMENT.

2. HiÓn thÞ danh s¸ch cña nh©n viªn thuéc sù qu¶n lý cña ng−êi cã tªn lµ 1 biÕn ®−îc nhËp tõ bµn phÝm

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ---------- ------- ------------- ---------- ----- ------ ---------- 7698 BLAKE MANAGER 7839 01-05-1981 2850 30 7654 MARTIN SALESMAN 7698 28-09-1981 1250 1400 30 7499 ALLEN SALESMAN 7698 20-02-1981 1600 300 30 7844 TURNER SALESMAN 7698 08-09-1981 1500 0 30 7900 JAMES CLERK 7698 03-12-1981 950 30 7521 WARD SALESMAN 7698 22-02-1981 1250 500 30

15 T¹o view

15.1 View

View lµ mét table logic, view kh«ng ph¶i lµ n¬i l−u tr÷ d÷ liÖu ë møc vËt lý. Çc thµnh phÇn cña view dùa trªn table hoÆc lµ trªn view kh¸c. Mäi t¸c ®éng lªn view ®Òu g©y ¶nh h−ëng tíi table cña view ®ã, vµ ng−îc l¹i. §Ó ®Þnh nghÜa mét view dïng query trªn mét b¶ng hay mét view nµo ®ã.

Có ph¸p

CREATE [OR REPLACE] [FORCE] VIEW view_name [(column, column,...)] AS SELECT statement [WITH CHECK OPTION [CONSTRAINT constraint_name]]; Trong ®ã OR REPLACE : ®Ó t¹o view chÌn lªn view cïng tªn FORCE : ®Ó t¹o view c¶ khi table hay view nµo ®ã kh«ng

tån t¹i trong c©u lÖnh SELECT. column, column, :Tªn çc column cña view WITH CHECK OPTION : nÕu cã lÖnh insert hoÆc update lªn vie−, ql sÏ

kiÓm tra ®iÒu kiÖn phï hîp trong mÖnh ®Ò where cña view. NÕu kh«ng d÷ liÖu sÏ chØ kiÓm tra çc rµng buéc toµn vÑn cña b¶ng.

CONSTRAINT : chØ ra tªn cña ®iÒu kiÖn kiÓm tra.




VÝ dô 1

CREATE VIEW emp_view

AS

SELECT empno, ename, sal FROM emp WHERE deptno = 10;

VÝ dô 2

CREATE VIEW dept_summary

(name, minsal, maxsal, avsal)

AS

SELECT dname, min(sal), max(sal), avg(sal) FROM emp, dept

FROM emp, dept

WHERE emp.deptno = dept.deptno

GROUP BY dname;

VÝ dô 3

CREATE VIEW dept_view

AS

SELECT eame, sal*12 Annsal

FROM emp

WHERE deptno = 20

WITH CHECK OPTIION CONSTRAINT dept_check;

Xãa çc view

ChØ nh÷ng ng−êi t¹o view míi cã quyÒn DROP

DROP VIEW dept_view;

View cã thÓ thùc hiÖn çc lÖnh SQL sau

• Select

• Insert (insert trªn view còng ¶nh h−ëng lªn table)

• Update (¶nh h−ëng lªn table)

• Comment

Tuy nhiªn cã nh÷ng rµng buéc sau:

• Kh«ng thÓ insert, update trªn view, khi query cña view chøa çc to¸n tö join, set, distinct, group by, group.

• Kh«ng thÓ nµo insert, update trªn view, nÕu nh− trong view cã dïng with check option.

• Kh«ng thÓ nµo insert trªn view, trªn table cã nh÷ng cét not Null mµ kh«ng dïng default value ( bëi v× trong tr−êng hîp nµy view sÏ cã Ýt colunm h¬n table table. Nªn insert 1 row vµo view, thùc chÊt lµ insert row ®ã vµo table sÏ kh«ng hîp lÖ).




• Kh«ng thÓ nµo insert trªn view, nÕu view nµy cã dïng biÓu thøc decode.

• Nh÷ng query cña view kh«ng thÓ nµo tham kh¶o vµo 2 column gi¶ nextval, currval (nextval, currval dïng cho sequence).

15.2 Bµi tËp

1. T¹o view cã hiÓn thÞ nh− sau:

select * from aggredates; DEPTNO AVERAGE MAXIMUN MINIMUN SUM NO_SALS NO_COMMS ------ ---------- ------- ---------- ---------- ---------- ---------- 10 2916.66667 5000 1300 8750 3 0 20 2235 3300 800 11175 5 0 30 1566.66667 2850 950 9400 6 4

2. T¹o view ®Ó nhËp sè liÖu vµo b¶ng ASIGNMENT víi çc ®iÒu kiÖn sau:

PROJID <2000, P_START_DATE<P_END_DATE Çc gi¸ trÞ cã thÓ chÊp nhËn cña assign_type lµ PS, WT hoÆc ED EMPNO cã gi¸ trÞ NOT NULL BILL_RATE < 50 Víi ASSIGN_TYPE Lµ PS BILL_RATE < 60 Víi ASSIGN_TYPE Lµ WT BILL_RATE < 70 Víi ASSIGN_TYPE Lµ ED

2. §Þnh nghÜa b¶ng MESSAGES cã cÊu tróc

Column name Data Type --------------------------------------------------- NUMCOL1 NUMBER(9,2) NUMCOL2 NUMBER(9,2) CHARCOL1 VARCHAR2(60) CHARCOL2 VARCHAR2(60) DATECOL1 DATE DATECOL2 DATE

16 QuyÒn vµ b¶o mËt

16.1 QuyÒn - PRIVILEGE

Privileges lµ çc quyÒn h¹n ®−îc thùc hiÖn çc thao t¸c hoÆc thùc hiÖn viÖc truy nhËp ®Õn çc ®èi t−îng d÷ liÖu. Trong Oracle b¹n sÏ kh«ng thÓ thùc hiÖn ®−îc çc thao t¸c mµ kh«ng cã çc quyÒn t−¬ng øng. Çc quyÒn h¹n nµy ®−îc g¸n cho User ®Ó cã thÓ thùc hiÖn çc thao t¸c trªn çc ®èi t−îng chØ ®Þnh. ViÖc g¸n quyÒn ®−îc thùc hiÖn bëi ng−êi qu¶n trÞ c¬ së d÷ liÖu.

G¸n quyÒn hoÆc lo¹i bá: §Ó thùc hiÖn g¸n quyÒn cho mét ®èi t−îng dïng lÖnh Grant lo¹i bá quyÒn h¹n dïng Revoke (hoÆc b»ng çc c«ng cô hç trî kh¸c nh− Oracle Enterprise manager)

Çc quyÒn bao gåm:

• B¶o mËt CSDL

• B¶o mËt hÖ thèng

• B¶o mËt d÷ liÖu

• QuyÒn hÖ thèng: QuyÒn truy nhËp vµ CSDL

• QuyÒn trªn ®èi t−îng: Thao t¸c nèi dung cña çc ®èi t−îng CSDL

• Schema lµ tËp howpjc ¸c ®èi t−îng nh− tables, view...

CSDL: Khi cµi ®Æt xong hÖ qu¶n trÞ CSDL ORACLE mÆc ®Þnh ®· cã 2 user.

• SYS: Cã quyÒn cao nhÊt. M¹t khÈu lµ change_on_install




• SYSTEM: Cã quyÒn thÊp h¬n SYS. MËt khÈu lµ MANAGER

QuyÒn hÖ thèng

Trong çc quyÒn hÖ thèng quyÒn DBA lµ lín nhÊt. DBA cã quyÒn

• CREATE USER : T¹o user míi

• DROP USER :Xo¸ user

• DROP ANY TABLE :Xo¸ table

• BACKUP ANY TABLE :T¹o çc backup table.

LÖnh t¹o user cña ng−êi cã quyÒn DBA nh− sau:

CREATE USER user_name IDENTIFY BY password;

QuyÒn trªn ®èi t−îng:

• CREATE SESION: Truy nhËp vµo CSDL

• CREATE TABLE: t¹o b¶ng trong user ®ã

• CREATE SEQUENCE: T¹o sequence

• CREATE VIEW: T¹o view

• CREATE PROCEDURE: T¹o procedure

• ...

G¸n quyÒn

GRANT privilege[,privilege...] TO user [,user...]

Xo¸ quyÒn

REVOKE privilege[,privilege...] FROM user [,user...]

16.2 ROLE

Role lµ tªn cña mét nhãm çc quyÒn h¹n. Nã ®−îc t¹o ®Ó qu¶n lý quyÒn h¹n cho çc øng dông hoÆc nhãm çc User. ViÖc dïng role cho phÐp qu¶n lý thèng nhÊt trªn çc ®èi t−îng, t¨ng tÝnh mÒm dÎo trong qu¶n trÞ, dÔ dµng thay ®æi. VÝ dô hai ®èi t−îng X, Y cã quyÒn trªn role A tøc lµ role A cã quyÒn g× th× X, Y cã quyÒn t−¬ng øng khi role A bÞ thay ®æi quyÒn h¹n th× X, Y còng bÞ thay ®æi quyÒn h¹n theo.

LÖnh t¹o Role:

CREATE ROLE role [IDENTIFY BY password];

G¸n privilege cho Role

G¸n Role cã çc ®èi t−îng

Mét sè Role hay dïng:

• CONNECT

• RESOURCE

LÖnh g¸n vµ xo¸ Role gièng nh− lÖnh g¸n vµ xo¸ Privilege. Chi tiÕt xem trong phÇn qu¶n trÞ ORACLE.




16.3 Synonym

Synonyms lµ bÝ danh cho mäi ®èi t−îng cña Oracle. Çc ®èi t−îng cña Oracle lµ table, view, snapshot, sequence, procedure, function, package vµ çc synonym kh¸c. Có ph¸p

CREATE PUBLIC SYNONYM synonym_name FROM [OWNER.]object_name;

Dïng Synonyms cã nh÷ng lîi ®iÓm sau:

• Kh«ng tèn thªm n¬i l−u tr÷ kh¸c bëi v× nã ®· ®−îc cÊt trªn tõ ®iÓn d÷ liÖu.

• Lµm ®¬n gi¶n ®o¹n ch−¬ng tr×nh SQL.

• T¨ng tÝnh b¶o mËt cho database.

• Cã thÓ cho phÐp mäi ng−êi (public) truy xuÊt çc ®èi t−îng cña Oracle.

VÝ dô: Chóng ta cã mét table EMPLY trong schema emp_01

Khi lËp tr×nh th× ph¶i truy xuÊt theo emp_01. EMPLY, tªn dµi nh− vËy th× ®o¹n ch−¬ng tr×nh sÏ dµi sÏ dÔ lÇm lÉn. Nªn chóng ta ph¶i dïng synonym

CREATE SYNONYM EMP FOR EMP_01.EMPLY;

Cã thÓ t¹o mét synonym cho phÐp mäi ng−êi cã thÓ tham kh¶o tíi

CREATE PUBLIC EMP FOR EMP_01.EMPLY;

TÝnh b¶o mËt lµ v× synonym lµ bÝ danh, nªn ng−êi sö dông dïng bÝ danh nµy sÏ kh«ng ®o¸n ®−îc thªm th«ng tin g×.

17 tæng quan vÒ pl/sql vµ procedure builder

17.1 Có ph¸p lÖnh PL/SQL

• Mçi lÖnh SQL kÒt thóc b»ng dÊu (;)

• LÖnh ®Þnh nghÜa CSDL (DDL) kh«ng ®−îc sö dông trong PL/SQL

• LÖnh SELECT tr¶ vÒ nhiÒu dßng cã thÓ g©y exception

• LÖnh DML cã thÓ t¸c ®éng trªn nhiÒu dßng

17.2 PL/SQL block

Khèi lÖnh PL/SQL gåm çc thµnh phÇn

DECLARE /Kh«ng b¾t buéc/

§Þnh nghÜa çc biÕn

BEGIN

§o¹n lÖnh;

EXCEPTION /Kh«ng b¾t buéc/

Hµnh ®ång nÕu lçi xuÊt hiÖn;

END;

VÝ dô 1

DECLARE

empno NUMBER(4):=7788;




BEGIN

UPDATE emp SET sal = 9000

WHERE empno = 0001;

....

END;

VÝ dô 2

DECLARE

v_deptno NUMBER(2);

v_loc VARCHAR2(15);

BEGIN

SELECT deptno, loc

INTO v_deptno, v_loc

FROM dept

WHERE dname = 'SALES';

END;

17.3 Giíi thiÖu Procedure builder

Trong Procedure Builder cã thÓ x©y dùng çc ®o¹n ch−¬ng tr×nh PL/SQL nh− program units, libraries, vµ database triggers ë c¶ client-side vµ server-side. Procedure Builder cã mét sè thµnh phÇn sau:

• Object Navigator lµ phÇn hiÓn thÞ mäi ®èi tîng trong Procedure Builder's

• Program Unit editor

• PL/SQL Interpreter

• Wizard

Object Navigator. §Æc tÝnh

• §ãng (+), më (-) çc node ®Ó xem th«ng tin

• Cã thÓ connect vµo CSDL ®Ó xem th«ng tin vÒ çc ®èi t−îng trong CSDL

• KÐo th¶ ®Ó copy ®èi t−îng

• T×m kiÕm ®èi t−îng

Program Unit editor

• T¸c dông: Dïng ®Ó so¹n th¶o ®o¹n ch−¬ng tr×nh PL/SQL dÔ dµng

• Çch gäi:

NhÊn ®óp vµo icon bªn tr¸i cña program unit. HoÆc

NhÊn ®óp vµo nót (+) ®Ó t¹o Program unit míi

• TiÖn Ých

Compile: DÞch




New: T¹o míi

Name: T×m theo çc program unit

Delete: Xo¸

Close: §ãng

Help: Trî gióp

Apply

Revert

PL/SQL Interpreter

• Khi chän mét program unit nµo ®ã. Néi dung cña program unit sÏ hiÖn lªn cöa sè Interpreter ®Ó debug.

• Cöa sè interpreter cßn cã phÇn ®¸nh lÖnh PL/SQL sau dÊu nh¾c PL/SQL>

Wizard

• Cöa sæ Wizard hiÓn thÞ khi t¹o mét program unit míi b»ng c«ng cô Wizard.

• C«ng cô nµy gióp dÔ dµng h¬n trong viÖc x©y dùng çc program unit.

T¹o mét program unit

• T¹o míi b»ng çch nhÊn vµo nót (+) trªn thanh toolbar.

• So¹n th¶o

Trî gióp so¹n th¶o b»ng menu edit.

Cã thÓ dïng import vµ export trªn menu file ®Ó ®−a thªm/lo¹i bá ®o¹n text

Chän Syntax palete trong menu program ®Ó trî gióp vÒ có ph¸p

Compile ®Ó t×m lçi, th«ng b¸o lçi hiÖn lªn t¹i dßng cuèi cña cöa sè

Database Trigger

• T¹o míi: NhÊn vµo nót (+), chän lo¹i database Trigger

• So¹n th¶o:

Gièng nh− víi Program unit

Thªm çc lùa chän thuéc tÝnh cña trigger.

T×m vÕt söa lçi çc Program Unit

• T×m vÕt, söa lçi çc Program Unit trong PL/SQL interpreter gåm cã:

Toolbar

Command line

• T¹o çc breakpoint (nhÊn ®óp vµo sè dßng lÖnh) ®Ó dõng ®o¹n ch−¬ng tr×nh, kiÓm tra çc biÕn runtime, d÷ liÖu...

• Çc c«ng cô trong interpreter

Step into: Thùc hiÖn tiÕp ®Õn dßng lÖnh tiÕp theo (cã thÓ ngoµi program unit)

Step over: Thùc hiÖn tiÕp ®Õn dßng lÖnh tiÕp theo nh−ng chØ trong Program unit ®ã.

Step out: Thùc hiÖn phÇn cßn l¹i cña ch−¬ng tr×nh

Go: Thùc hiÖn ®Õn cuèi ch−¬ng tr×nh vµ dõng l¹i khi cã breakpoint




Reset: Bá çc breakpoint.

Tæ chøc çc PL/SQL Program Unit

• Çc PL/SQL Program Unit th−êng ®−îc tæ chøc l¹i trong çc library (.PLL/.PPL).

Create: T¹o mét library míi

Open: Më library

Save: Ghi l¹i thay ®æi

• Attached library: Sö dông çc program unit trong çc Attached library nh− çc hµm mÆc ®Þnh.

• Stored Program Unit: CÊt Program Unit thµnh çc Stored Program Unit trong CSDL

18 có ph¸p lËp tr×nh

18.1 IF

IF condition THEN actions [ELSIF condition THEN actions] [ELSE actions] END IF

VÝ dô 1

IF ename := 'SCOTT' THEN

beam_me_up := 'YES';

COMMIT;

ELSE

beam_me_up := 'NO';

ROLLBACK;

END IF;

VÝ dô 2

IF choice= 1 THEN action := 'Run payroll';

ELSIF choice=2 THEN action:='Run';

ELSIF choice=3 THEN action:='Backup';

ELSE action:='Invalid';

END IF;

18.2 LOOP vµ EXIT

LOOP actions; [EXIT loop_label [WHEN condition]] END LOOP

VÝ dô 1:

LOOP

counter:=counter-1

INSERT INTO numbered_rows VALUES (counter);

.....

IF counter = 10 THEN




COMMIT;

EXIT;

END IF;

END LOOP;

VÝ dô 2:

LOOP

.....

EXIT WHEN total_sals = 60000;

....

END LOOP;

18.3 FOR

FOR control_variable IN [REVERSE] low_value .. high_value

VÝ dô

FOR I IN 1..2000

LOOP

INSERT INTO numbered_rows VALUES (i);

preserve_i:=i;

....

END LOOP;

18.4 WHILE

WHILE condition

VÝ dô

WHILE Bill<250

LOOP

actions;

END LOOP;

18.5 GOTO

GOTO label

VÝ dô

BEGIN

<<label1>>

.....

GOTO label1




19 cursor

19.1 §Þnh nghÜa

Cursor: lµ kiÓu biÕn cã cÊu tróc, cho phÐp ta xö lý d÷ liÖu gåm nhiÒu dßng. Sè dßng phô thuéc vµo c©u lÖnh query sau nã. Trong qu¸ tr×nh xö lý cursor nh− lµ mét con trá vÞ trÝ cña row ®ang xö lý

C¸c b−íc sö dông biÕn cursor: Khai b¸o -> më -> lÊy d÷ liÖu ®Ó xö lý -> ®ãng

Khai b¸o

cursor <ten( danh s¸ch biÕn)> is <c©u lÖnh select>: Më vïng d÷ liÖu cÊt tr÷ th«ng tin xö lý. vd: cursor x is select deptno from dept where deptno=10; vd: cursor x(b number) is select * from dept where deptno>b;

Më cursor

open <ten (trÞ cña biÕn)> vd: open x; vd: open x(10);

LÊy d÷ liÖu

Fetch <tªn cursor> into <tªn biÕn> Vd: fetch x into b;

§ãng cursor

Close <tªn cursor> vd: Close x;

C¸c thuéc tÝnh

%isopen : tr¶ l¹i gi¸ trÞ True nÕu cursor ®ang më

%notfound : tr¶ l¹i gi¸ trÞ True nÕu lÖnh fetch hiÖn thêi tr¶ l¹i kh«ng cã row

%found : tr¶ l¹i gi¸ tri true cho ®Õn khi fetch kh«ng cßn row nµo

%rowcount : tr¶ l¹i sè row ®· ®−îc thùc hiÖn b»ng lÖnh fetch

VÝ dô1:

declare cursor v_a is select * from emp; m v_a%rowtype; begin open v_a; loop fetch v_a into m; insert into t_thu(empno, ename,job) values (m.empno,m.ename, m.job); exit when v_a%notfound; end loop; close v_a; end;

vÝ dô 2:

DECLARE

CURSOR c1 IS SELECT dname, loc FROM dept FOR UPDATE OF loc;

dept_rec c1%ROWTYPE;

sales_count NUMBER:=0;

non_sales NUMBER:=0;




BEGIN

OPEN c1;

LOOP

FETCH c1 INTO dept_rec;

EXIT WHEN c1%NOTFOUND;

IF dept_rec.dname = 'SALES' AND dept_rec.loc!='DALLAS'

THEN

UPDATE dept SET loc='DALLAS' WHERE CURRENT OF c1;

sales_count:=sales_count+1;

ELSIF

dept rec.dname!='SALES' AND dept_rec.loc!='NEWYORK' THEN

UPDATE dept SET loc ='NEWYORK' WHERE CURRENT OF c1;

non_sales:=non_sales+1;

END IF;

END LOOP;

CLOSE c1;

INSERT INTO counts (sales_set, non_sales_set)

VALUES (sales_count, non_sales);

COMMIT;

END;

19.2 KiÓu d÷ liÖu Table vµ Record

KiÓu d÷ liÖu Table

Có ph¸p:

TYPE type_name IS TABLE OF datatype [NOT NULL] INDEX BY BINARY_INTEGER; var type_name;

VÝ dô

TYPE NAME IS TABLE OF EMP.ENAME%TYPE; First_name NAME; Last_name NAME;

KiÓu d÷ liÖu Record

Có ph¸p

TYPE type_name IS RECORD OF (Col1 datatype [NOT NULL{:=|DEFAULT} expr], (Col2 datatype [NOT NULL{:=|DEFAULT} expr]...); var type_name;

VÝ dô




TYPE emp_rec IS RECORD OF empno number(4) not null, ename char(10), job char(9), mgr number(4), hiredate date default sysdate, sal number(7,2), comm number(7,2), deptno number(2) not null ); Emp_record emp_rec;

19.3 Sao kiÓu d÷ liÖu

B¶n ghi trong PL/SQL. lµ mét biÕn cã thÓ gi÷ nhiÒu gi¸ trÞ vµ lµ mét tËp hîp çc biÕn t−¬ng øng víi çc tr−êng trong table.

§Ó ®Þnh nghÜa kiÓu d÷ liÖu b¶n ghi.

Var varref%ROWTYPE Trong ®ã Var : biÕn b¶n ghi Varref : Tªn b¶ng

VÝ dô:

X emp%ROWTYPE;

§Ó truy nhËp ®Õn çc tr−êng trong d÷ liÖu b¶n ghi dïng gièng nh− trong 1 row. VÝ dô

x.empno, x.sal...

§Ó sao kiÓu d÷ liÖu cña mét biÕn nµo ®ã.

X salgade%TYPE X sÏ cã kiÓu d÷ liÖu gièng biÕn salgrade.

19.4 C©u lÖnh SELECT... INTO... trong PL/SQL

Có ph¸p

SELECT col1, col2... INTO var1, var2... [cursor_var] FROM table1, table2... [WHERE condition1, condition2... ] [GROUP BY col1, col2 ...] [HAVING condition1, condition2...] [FOR UPDATE]; trong ®ã: INTO var1, var2... [cursor_var] ®Ó ®−a gi¸ trÞ trong table vµo trong çc biÕn ( cã thÓ lµ biÕn cursor ).

VÝ dô:

SELECT deptno, loc INTO v_deptno, v_loc FROM dept WHERE dname = ‘SALES’;

19.5 Bµi tËp

1. ViÕt ®o¹n ch−¬ng tr×nh t×m kiÕm çc hµng trong b¶ng EMP víi biÕn ®−îc ®−a tõ ngoµi vµo lµ &1 d¹ng JOb_type(emp.job%type)vµ ®−a ra th«ng b¸o thÝch hîp vµo b¶ng MESSAGES.




2. ViÕt ®o¹n ch−¬ng tr×nh ghi d÷ liÖu vµo b¶ng MESSAGES víi cét NUMCOL1 mang gi¸ trÞ lµ 1 nÕu lµ row 1 ®−îc Insert, 2 nÕu row 2 ®−îc Insert.... Kh«ng ®−îc Insert nh÷ng row cã gi¸ trÞ lµ 6 hoÆc 8, tho¸t khái vßng lÆp insert sau gi¸ trÞ 10. Commit sau vßng lÆp.

3. LiÖt kª çc cét ENAME, HIREDATE, SAL Víi ®iÒu kiÖn EMPNO b»ng gi¸ trÞ biÕn &EMPLOYEE_NO ®−îc ®−a vµo, sau ®ã kiÓm tra

- Cã ph¶i møc l−¬ng lín h¬n 1200

- Tªn nh©n viªn cã ph¶i cã chøa ch÷ T

- ngµy gia nhËp c¬ quan cã ph¶i lµ th¸ng 10 (DEC)

vµ ®−a gi¸ trÞ kiÓm tra nµy vµo b¶ng message cét charcol1 (thö víi çc gi¸ trÞ 7654, 7369, 7900, 7876)

4. §−a vµo vßng lÆp v tõ 1 ®Õn 10 lÖnh

UPDATE messages SET numcol2=100

WHERE numcol1 = v;

nÕu bÊt kú mét lÇn update nµo ®ã cã sè l−îng row >1 th× exit khái vßng lÆp.

20 procedure vµ funtion

20.1 Procedure

Lµ mét nhãm çc lÖnh thùc hiÖn chøc n¨ng nµo ®ã nh»m t¨ng kh¶ n¨ng xö lý, kh¶ n¨ng sö dông çc thñ tôc chung, t¨ng tÝnh b¶o mËt vµ an toµn d÷ liÖu, tiÖn Ých trong ph¸t triÓn.

Có ph¸p:

Procedure : Lµ tªn cña procedure ®−îc t¹o.

Argument : Gåm tªn cña danh s¸ch çc biÕn vµ kiÓu cña nã.

IN : ChØ ®Þnh r»ng b¹n ph¶i ®−a trÞ khi gäi procedure.

OUT : ChØ ra r»ng Procedure sÏ tr¶ l¹i trÞ cho biÕn tíi m«i tr−êng gäi nã.

IN OUT : ChØ ra r»ng b¹n ph¶i g¸n trÞ cho argument khi gäi procedure vµ procedure sÏ tr¶ l¹i trÞ

argument tíi m«i tr−êng gäi.

NÕu kh«ng ghi IN, OUT hoÆc IN OUT th× ngÇm ®Þnh sÏ lµ IN




Datatype : Lµ kiÓu cña argument, ë ®©y chØ ®−îc khai b¸o kiÓu mµ kg«ng ®−îc khai b¸o çc chiÒu dµi

argument. VÝ dô kh«ng ®−îc khai b¸o argument lµ VARCHAR2(10) mµ ph¶i khai b¸o lµ VARCHAR2.

Pl/sql_subprogram_body: Lµ phÇn th©n cña procedure ®−îc viÕt b»ng PL/SQL.

VÝ dô:

CREATE OR REPLACE PROCEDURE INS_DEPT(X NUMBER, Y VARCHAR2) IS BEGIN INSERT INTO DEPT(DEPTNO,DNAME) VALUES (X,Y); END;

Muèn thùc hiÖn procedure t¹i SQL plus thù hiÖn dïng lÖnh execute <ten(danh s¸ch gi¸ trÞ). Cßn trong çc

thñ tôc kh¸c dïng lÖnh gäi b×nh th−êng

SQL> execute ins_dept(55,’ New Name’);

20.2 Function

Có ph¸p:

Çc tham gièng nh− procedure nh−ng kh¸c lµ sau khi gäi hµm tr¶ l¹i trÞ

VÝ dô:

create or replace function get_dname( y number) return varchar2 is m char(14); begin select dname into m from dept where deptno=y; if SQL%notfound then m:='Khong thay'; end if; return(rtrim(m)); end;

§Ó gäi hµm get_dname ta gäi trùc tiÕp hoÆc th«ng qua çc phÐp g¸n.

VÝ dô:

SQL> select * from dept where dname=get_dname(10); DEPTNO DNAME LOC --------- -------------- ------------- 10 ACCOUNTING NEW YORK SQL> select get_dname(20) from dual; GET_DNAME(20) --------------------------------------------------------




RESEARCH

20.3 Bµi tËp

1. ViÕt hµm lÊy tªn gi¸m ®èc theo biÕn empno ®−îc nhËp vµo,

2. ViÕt thñ tôc nhËp th«ng tin vµo b¶ng message çc tr−êng

numcol1: M· phßng charcol1: tªn phßng ban numcol2: tæng l−¬ng cña phßng

3. ViÕt thñ tôc dïng cursor; lÊy sè liÖu vÒ n ng−êi (n lµ mét biÕn ®−îc ®−a vµo tõ man h×nh) cã møc l−¬ng cao nhÊt trong b¶ng emp ®−a vµo b¶ng top_sal víi çc gi¸ trÞ t−¬ng øng trong num=empno, name = ename, salary = sal). B¶ng top_sal cã cÊu tróc nh− sau:

NUM NUMBER(4) NAME VARCHAR2(25) SALARY NUMBER(11,2)

21 pakage

21.1 Package

Lµ tËp hîp cña çc ®èi t−îng gåm çc procedure, function, variable, constant, cursor vµ çc exception.

ViÖc t¹o çc package cho phÐp t¨ng kh¶ n¨ng mÒm dÎo, t¨ng tÝnh b¶o mËt, t¹o sù thuËn lîi trong viÖc qu¶n

lý hÖ thèng ®ång thêi t¨ng hiÖu suÊt xö lý cña hÖ thèng.

§Ó t¹o package thùc hiÖn nh− sau:

§Ó t¹o package body thùc hiÖn nh− sau:

Víi çc releases tr−íc ®©y cña PL/SQL viÖc gäi çc functions chØ cã thÓ ®−îc thùc hiÖn b»ng çc lÖnh cña

procedure, nh−ng giê th× çc lêi gäi nµy cã thÓ xuÊt hiÖn trong c©u lÖnh SQL gièng nh− lÖnh procedure. §iÒu

nµy cã nghÜa lµ ta cã thÓ sö dông çc functions gièng nh− çc built-in SQL functions. B»ng çc më réng SQL

ta cã thÓ tËp hîp ph©n tÝch ngay bªn trong Oracle Server mµ ta kh«ng cÇn lÊy d÷ liÖu vµo trong øng dông

®iÒu nµy lµm t¨ng tÝnh ®éc lËp cña c¬ së d÷ liÖu.

Tuy nhiªn ®Ó cã thÓ gäi ®−îc tõ SQL th× çc function ph¶i ®¶m b¶o ch¾c ch¾n viÖc kiÓm so¸t kÕt qu¶. Víi

çc standalone functions th× Oracle cã thÓ thùc hiÖn ®iÒu nµy b»ng viÖc kiÓm tra function body. Tuy nhiªn víi

body cña package lµ Èn cho nªn çc packaged functions ta ph¶i sö dông pragma

RESTRICT_REFERENCES ®Ó ®¶m b¶o luËt nµy.




Pragma Restrict_references(<Function/procedure Name>, <var1>, ...) Trong ®ã: WNDS: Write no database state RNDS: Read no database state WNPS: Write no package state RNPS: Read no package state

VÝ dô:

create or replace package vidu is function get_dname( y number) return varchar2; Pragma Resctrict_references(get_dname, WNDS, WNPS); Procedure ins_dept (x number, y varchar2); end vidu;

create or replace package body vidu is function get_dname( y number) return varchar2 is m char(14); begin select dname into m from dept where deptno=y; if SQL%notfound then m:='Khong thay'; end if; return(rtrim(m)); end; procedure ins_dept(x number, y varchar2) is begin insert into dept(deptno,dname) values (x,y); end; end vidu;

§Ó gäi ta thùc hiÖn nh− sau:

SQL> execute vidu.ins_dept(70,'Vi du');

22 database trigger

22.1 Database Trigger

Mét Database Trigger ®−îc t¹o vµ l−u tr÷ trong PL/SQL block t−¬ng øng víi table. Nã ®−îc tù ®éng gäi ®Õn khi cã sù truy nhËp ®Õn table t−¬ng øng víi c¸c hµnh ®éng ®Þnh nghÜa.

§Ó t¹o mét triger ta gâ theo cã ph¸p sau:




Create or replace : lÖnh t¹o hoÆc t¹o l¹i trigger nÕu nã ®· tån t¹i.

Before : ChØ ra r»ng trigger sÏ ®−îc thùc hiÖn tr−íc khi thùc hiÖn lÖnh.

Affter : ChØ ra r»ng trigger sÏ ®−îc thùc hiÖn sau lÖnh gäi tíi nã.

Delete, Insert, Update of <column> on <table>: trigger sÏ ®−îc gäi khi cã çc hµnh ®éng t−¬ng øng trªn tõng column cña b¶ng.

Referencing : ChØ tªn quan hÖ tíi çc trÞ cò (OLD) vµ míi (NEW) cña row .

For each row : Trigger thùc hiÖn t−¬ng øng víi mçi row cã ®iÒu kiÖn øng víi mÖnh ®Ò trong WHEN.

Pl/sql_block : Lµ khèi lÖnh PL/SQL thùc hiÖn çc xö lý theo mong muèn.

VÝ dô:

create or replace trigger t_dname before insert or update of dname on dept for each row when (new.dname is null) begin if (:new.dname is null) then :new.dname:='No Name'; end if; end ;

22.2 Bµi tËp

1. ViÕt trigger ®Ó khi nhËp sè liÖu vµo b¶ng emp th× nã còng nhËp sè liÖu vµo b¶ng emp1 víi ®iÒu kiÖn cÊu tróc b¶ng emp1 cã empno, ename, job, dname

2. Thªm 1 cét vµo b¶ng DEP tªn lµ SUMSAL. ViÕt trigger ®Ó cét SUMSAL lu«n chøa tæng l−¬ng cña phßng ban ®ã ( d÷ liÖu lÊy t−¬ng øng tõ b¶ng emp)

3. LËp 1 b¶ng tªn lµ BACKUP cã cÊu tróc gièng b¶ng EMP sao cho mçi b¶n ghi trong emp bÞ xo¸ sÏ l−u sang backup

4. øng víi çc theo t¸c insert, update, delete trªn b¶ng emp, l−u l¹i çc theo t¸c ®ã vµo b¶ng message, víi d÷ liÖu t−¬ng øng charcol1 = tªn thao t¸c, datecol2 = Ngµy giê thùc hiÖn.




23 error handing

Error handing lµ lçi xuÊt hiÖn trong khèi lÖnh PL/SQL, tÊt c¶ çc lçi nµy sÏ ch¹y vÒ phÇn EXCEPTION trong khèi lÖnh ®Ó xö lý.

Khèi lÖnh PL/SQL gåm çc thµnh phÇn

DECLARE /Kh«ng b¾t buéc/

§Þnh nghÜa çc biÕn

BEGIN

§o¹n lÖnh;

EXCEPTION /Kh«ng b¾t buéc/

Hµnh ®ång nÕu lçi xuÊt hiÖn;

END;

Có ph¸p thùc hiÖn çc EXCEPTION;

EXCEPTION WHEN exception1 [OR exception1. . .] THEN Xö lý; . . . [WHEN exception3 [OR exception4. . .] THEN Xö lý; . . .] [WHEN OTHERS THEN

Xö lý; . . .]

Trong ®ã: exception : tªn lçi n WHEN OTHERS : dïng ®Ó xö lý çc tr−êng hîp lçi kh¸c

§iÒu kiÖn kÝch ho¹t exception

Cã 2 nhãm exception:

• Çc exception cña b¶n th©n Oracle nh−: NO_DATA_FOUND, FOUND, TOO_MANY_ROW ...

• Çc exception do ng−êi sö dông khai b¸o

Çc exception hÖ thèng tù ®éng bÞ kÝch ho¹t trong çc tr−êng hîp nhÊt ®Þnh. Çc exception ng−êi sö dông ®Þnh nghÜa ph¶i tù kÝch ho¹t, vÝ dô

RAISE exception_identifier;

Mét sè exception hay dïng cña b¶n th©n Oracle:

Tªn M· lçi M« t¶

NO_DATA_FOUND ORA_01403 C©u lÖnh SELECT INTO kh«ng tr¶ vÒ row nµo

TOO_MANY_ROW ORA_01422 C©u lÖnh SELECT INTO kh«ng tr¶ vÒ lín h¬n 1 row

INVALID_CURSOR ORA_01001 Lçi xö lý CURSOR

ZERO_DIVIDE ORA_01476 Lçi chia cho 0




DUP_VAL_ON_INDEX ORA_00001 Lçi gi¸ trÞ bÞ trïng l¾p trong mét UNI QUE INDEX

VÝ dô Xo¸ nh÷ng nh©n viªn trong b¶ng emp nÕu t¹i phßng nh©n viªn ®ã lµm viÖc chØ cã mét nh©n viªn; trong Procedure buider

PROCEDURE DELEMP (V_EMP IN EMP.EMPNO%TYPE) IS V_ID EMP.EMPNO%TYPE; BEGIN SELECT EMPNO INTO V_ID FROM EMP WHERE EMPNO = V_EMP; DELETE FROM EMP WHERE EMPNO = V_EMP; COMMIT;

EXCEPTION WHEN NO_DATA_FOUND THEN ROLLBACK; TEXT_IO.PUT_LINE(TO_CHAR(V_EMP)||'KHONG CO');

WHEN TOO_MANY_ROWS THEN

ROLLBACK; TEXT_IO.PUT_LINE('CO LOI DU LIEU TRONG BANG EMP');

WHEN OTHERS THEN

ROLLBACK; TEXT_IO.PUT_LINE('CO LOI KHAC TRONG BANG EMP');

END;

Gäi ch¹y delemp(7364);

Çc exception do ng−êi sö dông ®Þnh nghÜa

Khai b¸o exception

identifier EXCEPTION;

VÝ dô:

DECLARE

credit_exceeded EXCEPTION;

BEGIN

IF stock_ordered > credit_limit THEN

RAISE credit_exceeded;

END IF

....

EXCEPTION

WHEN credit_exceeded THEN ....

END;

§Æt tªn cho çc exception hÖ thèng

Mçi exception hÖ thèng ®−îc g¸n mét sè x¸c ®Þnh, cã thÓ ®Æt tªn cho çc exception ®Ó dÔ sö dông h¬n.

PRAGMA EXCEPTION_INIT (exception_identifier, number)




VÝ dô

DECLARE

fetch_failed EXCEPTION;

PRAGMA EXCEPTION_INIT (fetch_failed, -1002);

BEGIN

....

EXCEPTION

WHEN fetch_failed THEN ....

END;

23.1 Bµi tËp

1. Dïng EXCEPTION b¾t lçi chÆt h¬n cho c¸c bµi tËp tõ phÇn 19-22.

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