ligjeratat ne baza e te dhenave

8/10/2019 Ligjeratat Ne Baza e Te Dhenave

http://slidepdf.com/reader/full/ligjeratat-ne-baza-e-te-dhenave 1/436

nbraha-bazat e te dhenave 1

ani e programi ibazave te te dhenave me

zbatim ne MYSQLBazat e punes ne access (ketupermenden elementet themelore

dhe puna me to )Urdherat themelore neSQL(structural query

language)(ketu mesohen urdheratthemelore dhe manipulimet me tone SQL( te pergjithshem) ,ndersa

ushtrimet organizohen ne MYSQL)




Menyra e vleresimit

10% nga vijueshmeria .

25% nga seminari i cili punohetkryesisht ne ushtrime laboratorike(d.m.th ne laborator ), punohet ne

access dhe dorezohet me se largu nje jave pa perfundu ligjeratat esemestrit III .

65 % nga provimi perfundimtare (i cilimbahet ne fund te semestrit ).




Literatura

Literatura :1.Mastering access , Autore:AlanSimpson,Celeste Robinson ,Botimi

19992.Database system conceptsAutore :Abraham Silberschatz,HenryF.Korth,S.Sudarshan,Botimi 20013.Microsoft server 20004.Database modeling and designautore:Toby .J.Teorey,botimi 1999

(gjindet ne biblioteke)


http://slidepdf.com/reader/full/ligjeratat-ne-baza-e-te-dhenave 4/436nbraha-bazat e te dhenave 4

Literatura5. Mannual-sql (manual I mysql-se ne web ne adresenwww.mysql.com)

6.Database process,autore :DavidKroenke(gjindet ne biblioteke)7.Access bible 2002 ,autoreMichael Irwin ,Cary Prague8.Teach yourself sql (botim ngaSAMS)

http://www.mysql.com/





Bazat e te dhenave

Ç‘eshte baza e tedhenave

Per cfare sherben

Si ndertohet



Kriteret qe merren parasysh

ne nje baze―Data Redudancy―(perseritja e tedhenave )Gjate ndertimit te bazes

se te dhenave ,nga disa personamundet qe nje fajlle (tani etutje tabela) i njejte te

perseritet p.sh nje e dhene―emri‖.Keshtu ne bazen e tedhenave fitojme perseritje te tedhenave ,kjo njihet me emrin

―redudancy‖.




Data redudancyNje redudance e te dhenave eshtebere ne shembullin qe do teshohim ne vijim ,ku e dhena e

emrit ne nje lidhmeri teentiteteve eshte perseritur dhesi e tille eshte e palejueshme.

Kjo shihet ne diagramin eparaqitur me poshte dhe kjoperseritje eshte bere ne teretabelat e shqyrtuara (atributiemri) .




Data redudancy(vazh.)




―Veshtirsia ne qasje‖

Nese merret nje shembull I ndertimitte nje programi per pune bankare ,sicdihet ne te duhet te kemi nje aplikimper vendosje te klienteve ,perbalance te te ardhurave etj dhekerkohet nje e dhene qe te kihet

regjistri I te dhenave te klienteve qe jane nga ―tirana‖ .Nese ne ate programnuk eshte aplikacioni i kerkesave njegje te tille nuk mundemi me e pase

d.m.th kemi nje veshtiresi ne qasje tete dhenave .Kete e ilustron ky diagrami meposhtem.




Veshtirsia ne qasje(vazh.)




Veshtirsia ne qasje(vazh.)Siq shihet me siper mundesia ekerkimit te te dhenave nuk eshte

e mundur pasi nje gje e tille nukeshte parapare ne kuader te asajforme kerkuese,qe d.m.th se kemi

veshtiresi ne qasje




―Data isolation‖

Nese kemi te dhenat nga disafajlla me forma te ndryshmeateher nje qasje e te dhenave neate baze do te ishte e veshtirepasi kemi informata te izoluara




―integrity problem‖ Nese kemi te bejme me nje klientete bankes dhe per ate dhe klientettjere kemi vendose qe ne llogarine e

tije te kete me se paku 30 eurogjate terheqjes se parave ngallogaria ateher kemi te bejme me njepjese te programit e cila mundesonnje te dhene te tille ,tani venja elargimi i nje kushti te tille na paraqetproblem ,keto paraqesin nje integritet

referencial te te dhenave




―Atomicity of data‖ Problemi I tille ne kuader te nje baze tete dhenave paraqitet nese kemi te bejmeme dergim te nje llogaria nga klienti 1 neate te klientit 2 dhe nese gjate ketijtransferi na largohet shuma nga klienti1por nuk paraqitet te klienti 2,d.m.th

humben te dhenat .Gjate bartjes se tedhenave duhet ajo te jete ―atomike ―d.m.thqe bartja te behet brenda atij entiteti.




―concurrent access anomalies‖

Nese ne kuader te nje banke kemishumen prej 80 eurove ne nje llogaridhe njekohesisht nga e njejta llogaridy persona (klient) terheqin ne tenjejten kohe shumat p.sh 50 dhe 40nga po e njejta shume ,ateher llogaria

e tille e larte shenuare mbetet ne njepozite inekzistente ,per kete sistemiduhet te kete nje supervision i cilibene nje kontrolle te tille .Kjo na

paraqet nje anomali gjate qasjeparalele te te dhenave




―security problem‖ Nese meret shembulli I bankes ateherprogrami te cilin e kemi duhet qe timundesoje klienteve vetem te keneqasje ne gjendjen e llogarise se tyredhe parashtrimit te kerkesave nelidhje me te por jo edhe te

nderhyrjes se tyre ne vet gjendje ,kjoarrihet me ane te sigurimit te tedhenave ne kuader te asaj baze te te

dhenave




Siguria e te dhenave(vazh.)Nje gje e tille do te ishte erealizueshme nese ne shembullin

e shikimit te te dhenave ngaforma e paraqitur me pare te moskishim mundesi te nderhyrjes ne

vet programin e ndertimit tebazes .




―shikimi i te dhenave ‖

Abstrakcioni i te dhenave

Qasja dhe skema e te dhenave

Pavaresia e te dhenave

b k dh




Abstrakcioni i te dhenaveShfrytezuesit e bazes se te dhenave

duhet ti paraqitet baza ne ate menyreqe ai ta kete me te lehte per meperdore kjo arrihet permes disa

niveleve te organizimit te te dhenaveNiveli fizike I te dhenave –ky eshteniveli I pare I shikim te te dhenavedhe ketu jane te dhenat e pershkuara

ne detale se si jane te vendosuraNiveli logjike-ketu pershkruhen

lidhmerite dhe rrolet e te dhenave ,ne

veqanti nga administratori I bazes sete dhenave

Abstakcioni i te dhenave (1)




Abstakcioni i te dhenave (1)Niveli i shikimit –ky ne radhe te pare na

mundeson nje shikim te nje aplikacioni teprogramit por jo edhe detalet e tipevete te dhenave dhe te dhenave ne

pergjithesi .P.sh nje puntore banke i cilipunon ne kabine per dhenie dhe marrjene te hollave ka mundesin e shikimit te te

dhenave por jo edhe te te dhenave detale,perkatesisht per modifikim te vetbazes se te dhenave .Nje ilustrim I

kesaj do te ishte

Ab t k i i i t dh (2)




Abstrakcioni i te dhenave(2)




Pavaresia e te dhenave

Aftesia e ndrrimit te skemes sete dhenave nga nje nivel dhe I cili

nuk ndikon ne skemen e te dhenavene nivelin tjeter ,paraqet pavaresine te dhenave .Jane dy nivele te

pavaresise se te dhenave1.niveli fizike dhe

2.niveli logjike

Mo e et e bazave te te




Mo e et e bazave te tedhenave

Me model te te dhenavenenkuptojme teresine e veglaveper pershkrim te :

1. Te te dhenave2. Te lidhjeve te tyre3. Semantiken e te dhenes

4. kushtezimetNe varesi nga pershkrimi i

mesiperm kemi keto lloje te

bazave te te dhenave

―entity relation model‖




entity relation model Nje modele I tille do te pershkruhejme pershkrim reale te te dhenave i cilipershkruhet me ,objekte bazike tequajtura entitete , lidhmerise se tyre

si dhe atributet p.sh nje entitet mundte jete personi qe punon ne banke dheketo jane te pershkruara me atributep.sh ai te punoje ne kabine,ndersa

lidhmeria e tyre do te ishte mes disaentiteteve .Keto modele shkurt do tishenojme me E-R.Pershkrimi i tedhenave ne kuader te nje E-R do teparaqitej ne keto pika kryesore

E R d li




E-R modeliBashkesia e entiteve

Lidhmeria e tyre

Paraqitja e Dizajnit

Kufizimi i te dhenaveQelesat

E-R Diagrami

Veglerit e zgjeruara te E-R

Dizajni i nje E-R baze

Kthimi i nje E-R modeli ne formetabele

Obj k ( i )




Objektet (entitetet)

Nje baze mund te modelohet si :Bashkesi e entiteteve ,Relacionet ne mes tyre.

Nje objekt eshte nje objekt ekzistues dhe icili dallon nga nje tjeter.Psh nje person i caktuare ,fabrika etjKeto objekte kane vetite e tyre (atributet)

Psh :njerzit kane emer dhe mbiemer etj Nje bashkesi e entiteteve eshte ajobashkesi e cila ka tipe te njejte dhe qe

ndajne veti (atribute) te njejta ne mesvete.Psh : bashkesia e te gjithe njerezve (kane tegjithe emra,mbiemra etj),bashkesia e te gjitha

fabrikave etj

Bashkesia e entitetit‖loan‖




Bashkesia e entitetit loan customer-id customer- customer- customer- loan- amount

name street city number

Atributet




AtributetPershkrimi i nje objekti mundesohet permesshume vetive (atributeve)

Domeni i atributit – bashkesia e vlerave temundeshme te atributeveTipet e atributeve :

Atributet e drejtperdrejta (thjeshta) dhe ato tederivueme (ato qe rrjedhin nga ato te parat) .Ato te parat jane te njevlershme dhe teshumevlershme

Psh shumevlershme :numrat e kartelave te bankes etjAto te derivueshme

Merren nga ato te paratPsh mosha e marre nga data e lindjes

Psh :

bleresi (customer) = (customer-id, customer-name,customer-street, customer-city)

huaja (loan) = (loan-number, amount)

Atributet e derivueme




Lidhmeria e te dhenave




L hm r a t h naLidhmeria e te dhenave realizohet per disaobjekte

Psh :Hayes depositor A-102

me kete behet lidhmeria e bleresit

(customer) dhe llogarise se tije .Lidhmeria ndermjet e objekteve eshte njerelacion matematike i me teper se 2objekteve ,i marre si nenbashkesi e{(e 1, e 2, … e n ) | e 1 E 1, e 2 E 2, …, e n E n }

ku (e 1, e 2, …, e n ) eshte nje qifte i atributeve

psh : (Hayes, A-102) depositor

Nje lidhje ne mes te marresit




j j m mdhe huadhenesit

Lidhmeria e objekteve




jNje paraqitje e nje lidhje ne mes teobjekteve eshte paraqitur edhe ne kete

skeme ,dhe objekti depozitor mund te ketedhe atributin ―data-access‖

Shkalla e lidhjes se objekteve




j jKjo paraqet numrin e entiteteve qe

marrim pjese ne nje lidhje.Relacioni ne te cilin marrin pjese dyentitete quhet binar ,tri ternar etj.

Ne nje lidhje mund te futen me teperse dy entitete .

Lidhjet ne mes te me shume se 2entiteteve jane te rralla

Psh nje i punesuar ne banke mund te kete punene disa filialla, atehere kemi nje lidhje ternare nemes te entiteteve te punesuar ,punet dhe fillialle

Tipet e lidhjeve ne mes te




p jentiteteveMeqe shumica e lidhjeve ne mes teentiteteve eshte lidhje binare ateherme poshte do te pershkojme tipet elidhjes ne mes tyre.Tipet themelore te lidhjes ne mes te

entiteteve jane keto :Nje me nje (One to one)

Nje me shume (One to many)

Shume me nje (Many to one)Dhe shume me shume (Many to many )

Tipet e i jes- nje me nje ej h




p j j jnje me shume

Lidhja nje me nje Lidhja nje me shume

shenim:disa nga elementet ne A dhe B mund te mos jene te perfshira neLidhje

ipet e i jes–s ume me njedh h h




p j jdhe shume me shume

Shume me nje Shume me shume

Diagrami i nje E-R-je




g j j

Drejtekendeshi –paraqet nje entitet .

Paralelogrami –nje lidhje ne mes te entiteteve .

Vizat –lidhjet ne mese te entitetit dhe atributit si dhe nemes te entiteteve permes lidhjes .

Elipsat -paraqesin atribute

Elipsat e dyfishta-paraqesin atribute te shumfishta .

Elipsat e nderprera –atributet e derivuara .

Te nenvizuara –atributet kryesore (qelesat )

Pershkrimi i elementeve te




nje ER-je

Nje E-R me i komlikuar




Nje E R me i komlikuar




Lidhmerite me atribute

Rrolet e objekteveEntitetet e nje lidhje nuk duhet te jen




Entitetet e nje lidhje nuk duhet te jenme veti te ndryshme

Ne vizat e meposhtme ―manager‖ dhe―worker‖ paraqesin rrolet;ata specifikojne sesi entiteti ―employee‖ komunikon me ― works-for‖ ne ate lidhje.

Rrolet ne nje E-R shenohen me shkronja nevizat qe i lidhin entitetet dhe kushtit telidhjes .Rrolet me labela zgjedhen sipas deshires dhemerren vetem per kjartesi te semantikes

Menyrat e shenimit te lidhjes




y jLidhja nje me shume do te shenohet me (),

ku njeshin e paraqet fillimi i vizes ndersashumicen mbarimi ,viza (—) e pa orientuareparaqet lidhjen shume me shume e orientuarenga kushti i lidhjes ne drejtim te entitetit.

Psh : nje me nje :Bleresi eshte i shoqeruare me se paku nje hua(loan) permes huadhenesin (borrower)Njesoj huaja eshte e lidhur me te pakten njebleres permes te huadhenesit (borrower)

Nje me shume




Ne lidhjen nje me shume huaja( loan)

eshte lidhur me te pakten nje blerespermes ―borrower‖,ndersa bleresieshte i lidhur me disa huaja permes te

―borrower‖

Shume me nje




Ne kete raste kemi mundesin e

kundert me ate te mare ne rastin emesiperm.

Shume me shume




Ne kete raste ana e bleresit eshte elidhur me shume hua permes te―borrower‖ dhe anasjelltas huaja kashume bleres

R li i t lidhj




Realizimet e lidhjeve

Ne lidhjet e mesiperme duhetcekur se kusht themelore eshte

qe ato te dhena te cilatdeshirojme ti lidhim te kene tipete njejte te te dhenave (ku tipi i

te dhenave do te permendetedhe ne vazhdim )

Pjesemarrja e nje entiteti nenje lidhje




nje lidhje Pjesemarrja totale ne nje lidhje (e shenuar e me viza te dyfishta ): kjo merret

ne ate raste kur secili entitet merr pjese ne te pakten nje lidhje ne ate lidhmerite entiteteve

Psh pjesemarrja e huase (loan) ne “borrower” eshte totale

secila hua duhet te kete nje bleres(costumer) permes te “borrower”

Pjesemarrja e pjesshme : disa entitete mund te mos marrin pjese ne te gjithalidhjet ne ate baze

Psh pjesemarrja e “customer” ne “ borrower” eshte e pjesshme

Qelesat (Keys)Le te jete K R




Le te jete K RK eshte nje ― superkey” i relacionit R nesevlerat e K jane te mjaftueshme peridentifikim te nje qifti te mundshem ngarelacioni r(R)

Ku me relacion te mundshme nenkuptojme nje qift icili mund te krijohet ne ate model.Psh : {customer-name, customer-street } dhe

{customer-name }

jane ―superkeys‖ te ―Customer‖ ,nese dy―customer‖ nuk kane emra te njejte.

K eshte ―candidate key ― nese K eshteminimal

psh : {customer-name } eshte ―candidate key‖per ―Customer‖ ,perderisa ai do te jete―superkey‖ (nen supozimin se dy ―customers‖nuk kane emer te njejte ) dhe nese

nenbashkesit e ti e nuk ane ―su erke ‖

Fushat kryesore dhe rroli i tyrene lidhjen e entiteteve




ne lidhjen e entiteteveKombinimi i qelesave kryesore te entiteteve me

pjesemarrje te pjesshme ne nje lidhje formojnenje ―super key‖.

Psh (customer-id, account-number ) eshte nje ―superkey‖ per tabelen ―depositor‖

Shenim: kjo nenkupton se qiftet e entiteteve kanete pakten nje lidhje ne bashkesine epjesshme telidhjes.

Psh nese percjellim te gjitha qasjet e te dhenave nesecilin llogari (account) nga secili ―customer‖, ne nuk mundte supozojme lidhje per secilen qasje.Edhe pse ne mundte marrim atribute me shumevleraGjithashtu gjate percaktimit te ―candidate key‖-ve duhette kihet parasysh edhe lidhmeria e te dhenave ne atoentitete

Gjate percaktimit te ―primary key ‖ nebashkesine e lidhjeve me me shume se nje―candidate key ‖ ne kuader te nje pyetsore kjo

duhet edhe te ceket ne semantiken e tij

Realizimi i lidhjeve ne access




Realizimi i lidhjeve ne accessMe nje shembull shohim nevazhdim lidhjet e tipeve tepermendura

1.nje me njeKjo realizohet ndermjete fushave

kryesore te atyre dy entiteteve

Lidhja nje me nje




Lidhja nje me nje (vazh.)




Lidhja nje me nje(vazh)




Lidhja nje me nje (vazh )





Lidhja nje me shume




Lidhja nje me shume

Kjo lidhje ne access realizohetper dy entitete ashtu qe ne

tabelen e pare ku deshirojme tekemi lidhjen nje duhet te kemifushen kryesore ,ndersa ne te

dyten ku deshirojme te kemilidhjen shume duhet te jete fushe jokryesore,kjo shihet me kete

shembull,ndermjet tabelave 1 dhetabeles 2. gjithashtu duhet teceket se tipet e te dhenave duhet

te jen te njejta

Lidhja nje me shume




Lidhja nje me shume

Lidhja shume me shume




Kjo lidhje ne access realizohet nemes te dy atributeve jo kryesoreduke ndertuare nje tabele ndihmese

e cila perbehet nga atributetkryesore te dy tabelave ne lidhjedhe i ka qe te dy ato si atribute

kryesore,sic shihet ne shembullin emeposhtem ,ku behet realizimi ilidhjes ne mes te tab1 dhe tab2.

Lidhja shume me shume(vazh )




Lidhja shume me shume(vazh.)

Lidhjet jo binare




Lidhjet jo binare

Me siper u pa se si behet lidhja e

entiteve dhe realizimi i tyre neAccess per ato entitete te cilat jane ne lidhmeri binare ne mes

veti .Ne vazhdim shohim se ckandodhe me ato entitete te cilatkane lidhje te rendeve tjera .

Shembull i diagramit E-R menje lidhje ternare




j j

Shembull i diagramit E-R me




nje lidhje ternareSic shihet nga shembulli i mesipermlidhja ternare eshte realizuare nemes te entiteteve ―job‖,‖employ‖ dhe―branch‖.E gjithe kjo eshte realizuarepermes ―works on‖.

Lidhmeria ne nje relacionternare




ternare

Ne nje relacion ternare (ose n-are) sepaku nje lidhje ne mes te tyre lihetanash per te percaktuare lidhjen ne

mes te dy entiteteve qe marrin pjesene ate lidhjePsh nje lidhje ne mes te ―works-on ―

dhe ― job‖ paraqet faktin se secili―employee‖ punon se paku ne nje ―job‖ne cilendo ―branch‖ Nese aty merren me shume se nje

lidhje ateherë kemi dy menyra tepercaktimit te kuptimit ne mes tyre.

Lidhmeria ne nje relacion




ternare(vazh)Psh nje relacion ternare R ne mes te entitetevelidhese A , B dhe C me lidhje ne B dhe C mundte kuptohet si1.secili entitet ne kete rast A eshte i percaktuare ne menyre te vetme me entitet Bdhe C ose2.secilit qift te entiteteve nga (A, B ) ipergjigjet nje i vetem C dhe secilit qift nga (A,

C ) nje i vetem BSecila alternative eshte marre ne menyra tendryshme

Per kete arsye ne largojme nje ose me shumelidhje ne relacionet ternare (n-are) gjaterealizimit te lidhjes .



Paraqitja binare e lidhjeve qenuk jane binareNe per jithesi secili relaci n j binare mund te




Ne pergjithesi secili relacion jo binare mund te

shprehet permes atyre binare duke krijuarenje entitet artificial.Kjo behet keshtu

Zevendesohet R ne mes te entiteteve A, B dhe C

me nje entitet E , ateher merren keto lidhje te reja:1. R A , per E dhe A 2.R B , per E dhe B

3. R C , per E dhe C

Duhet krijuar edhe disa atribute lidhese ne ESe pari duhet te shtohen ter atributet e R ne E

Per cdo relacion lidhje (a i , b i , c i ) ne R, krijohet

1.Nje entitet i ri e i ne bashkesine e entiteteve E2.Shtohet (e i , a i ) ne R A 3.Shtohet (e i , b i ) neR B 4.shtohet (e i , c i ) ne R C

Paraqitja binare e lidhjeve qenuk jane binare me nje ‗E-R‘




j j

diagram

Paraqitja binare e lidhjeveqe nuk jane binare




Gjithashtu duhet te pershtaten

kufizimet ne lidhjen e rePershtatja e te gjitha kufizimeve mundte jete e pamundur

Ne paraqitjen e re mund te kemi asi rastekur ne skemen e vjeter mos ti pergjigjetasnje,mirepo per kete duhet te veprohetkeshtu:

Psh : me i shtue kushtet e reja ne R A , R B dhe

R C qe te sigurohemi se entiteti i ri ti pergjigjetnjerit nga entitetet ne A, B dhe C



Shembulli i njerelacioni,tabela ―account‖




Struktura bazePer bashkesite e dhena D 1, D 2, …. D n njerelacion r eshte nenbashkesi e




relacion r eshte nenbashkesi e

D 1 x D 2 x … x D n d.m.th relacioni i gjatesise n eshte nje qift irenditur (a 1, a 2, …, a n ) ku secila a i D i

Psh :nese customer-name = {Jones, Smith, CurryLindsay}customer-street = {Main, North, Park}customer-city = {Harrison, Rye, Pittsfield}

ateher r = { (Jones, Main, Harrison),(Smith, North, Rye),(Curry, North, Rye),(Lindsay, Park, Pittsfield)}

eshte relacion i gjatesise 3 me atributetcustomer-name x customer-street x customer- city

Tipet e atributeveSecili atribute eshte i emeruare




Secili atribute eshte i emeruareBashkesia e vlerave te lejuara te atributitparaqet domenine e atributitVlerat e atributeve kerkohet te jene

atomike, kjo do te thote te pandashmePsh atribute me shume vlera nuk janeatomike

Psh vlerat e atributeve te kompozuara nuk jane atomikeNdersa vlera zerro eshte pjese e secilitdomeneVlera zerro sjell komplikime ne definimin eshume operatoreve

ne vijim do te injorojme vlerat zerro dhe do ti

shohim me vone

Skema Relacionale




Nese A 1, A 2, …, A n jane atribute,ateherR = (A 1, A 2, …, A n ) paraqet nje skeme

relacionalepsh Customer-schema =

(customer-name,

customer-street, customer-city )Me r (R ) do te shenojme nje relacionne skemen relacionale

psh customer (Customer-schema)

Shembull i nje relacioniVlerat e nje relacioni jane te




Vlerat e nje relacioni jane te

specifikuara permes te tabelaveKu nje element (t) nga r eshte njecifte i paraqitu me nje

rresht(record) ne kuader te tabeles

JonesSmithCurry

Lindsay

customer-name

MainNorthNorthPark

customer-street

HarrisonRyeRye

Pittsfield

customer-city

customer

atributet(ne kolona)

Ciftetne rreshta



Baza e te dhenaveBdh perbehet prej disa relacioneveInformatat per nje fabrike ndahen ne pjese




Informatat per nje fabr ke ndahen ne pjese

ne disa relacione ku secili nga ta paraqet njeinformatePsh : account :paraqet informata ne lidhjeme llogarite ne ate firme

depositor : paraqet te dhenat nelidhje me depozituesitcustomer : paraqet informatat ne

lidhje me klientet

Paraqitja e te dhenave ne nje relacion si nebank (account-number, balance, customer- name , ..)rezulton ne

Perseritjen e te dhenave (psh dy kliente me njellogari)Paraqitja e vlerave zerro (psh paraqet klientin qenuk ka llogari)

Pershtatja e bdh




Ne gjithe problemet e paraqitura

me larte ,zgjidhjen e tyre do tamarrim me normalizimin e bdh qedo te shihet me vone .

Relacioni ―customer‖




Relacioni ―depositor‖




E-R Diagrami per nje banke




Skema e Diagramit per banke




Gjuha e pyetsoreve (QueryLanguages)




Kjo eshte gjuha me te cilen ipen dhemerren te dhenat nga bdh.

Kategorite e gjuheve

proceduraleDhe jo-procedurale

Gjuhet e pastra (―Pure‖ languages):

Algjebra relacionaleNjehsimet me ciftet relacionale

Domeni i njehsimeve relacionale

Algjebra RelacionaleEshte gjuhe procedurale




Eshte gjuhe proceduraleKeto jane operacionet themelore

Selectproject

unionset differenceCartesian productrename

Veqori e ketyre operacioneve eshtese marrin si te dhena hyrese disarelacione dhe japim vetem nje relacion

ne dalje si rezultate.

Shembull i operacionit Select




• Relacioni r A B C D

1

5

12

23

7

7

3

10

• A=B ^ D > 5 (r) A B C D

1

23

7

10

Shembull i operacionitSelect(vazh.)




• A=B ^ D > 5 (r) me ane te relacionit te mesipermeshte mundesue te behet zgjedhja e te

dhenave nga relacioni r me kushte qe ato te

dhena te plotesojne keto kushte:

• 1.qe A te jete sikurse B

• 2.dhe qe ne ate relacion r kushti D te jete me i

madhe se sa numri 5 dhe sic u pa me lartenje gje te tille e plotesojne rreshti i pare dhe i

fundit ne relacionin r.

Operacioni ―Select‖ Shenimi : p (r ) do te thote :




p

p paraqet predikatin zgjedhes ne ate relacion Definohet si me poshte :

p (r ) = {t | t r dhe p(t) }

ku p eshte nje formule me kushtet ezgjedhjes qe permbane ne vete shprehjet elidhura me relacionet : (dhe (and)), (ose

(or)), (mohimin (not))secili nga termet eshte njeri nga :<attribute> dicka <attribute> ose <constant>

ku dicka paraqet : =, , >, . <. Shembull i operacionit ―select‖ eshte ky : branch- name=―Perryridge ‖ (account )

Operacioni ―select‖




Ne shembullin e fundit

mundesohet shikimi i te dhenavete llogarive(account) nga filiallame emer (branch) ―Perryridge‖

Operacioni ―Project‖




Relacioni r :

A B C

10

20

30

40

1

1

1

2

A C

1

1

1

2

=

A C

1

1

2

A,C (r )

Operacioni ―Project‖




shenim:me relacioni A1, A2, …, Ak (r )ku A 1 , A 2 jane emrat e atributeve jane marreatributet e cekura ne relacionin r .

Veprimi qe kryhet eshte ky merren k kolonate cekura duke i perjashtuare te tjeratVlerat e njejta (te shumfishta ) ne kuader te

rreshtave gjithashtu perjashtohenPsh per te eliminuare emrin e filialles (branch- name) nga llogaria (account) marrim si me

poshteaccount-number, balance (account )



Operacioni ―Union‖ Shenimi : r s

Definohet sikurse :




r s = {t | t r ose t s }r s eshte i vertete (i realizueshem) kur

1. r, s kane numer te njejte te atributeve

2. Domenet e atributeve duhet te jenekompatibile ne mes veti (psh , kolona e 2-tenga relacioni ka tipe te njejte te vlerave mekolonen 2 nga s )Psh . Gjeni te gjithe ―customers‖ me llogari

(account) ose hua (loan)

customer-name (depositor ) customer-name

(borrower)

Ndryshimi ne mes tebashkesive




Relacionet r, s:

r – s:

A B

1

2

1

A B

2

3

r

s

A B

1

1

Ndryshimi ne mes tebashkesive




Shenimi r – s Definohet si :r – s = {t | t r dhe t s }

Ndryshimi ne mes te bashkesiveduhet te merret ne mes te relacioneve

kompatibile dhe pershkrimi ishembullit larte eshte ky:jane marreato cifte te relacionit r dhe janelarguare nga r ato qe jane edhe ne s.

r dhe s duhet te kene te njejten gjatesiDomenet e atributeve duhet te jenekompatibile



Produkti kartezian

h




Shenimi r x s Definimi eshte :r x s = {t q | t r dhe q s }

Supozohte se atributet nga r(R) dhes(S) jane disjunkte. (d.m.thR S = ).

Nese atributet e r(R) dhe s(S ) nuk janedisjunkte ,ateher ato qe mbesin duhet temerren.Pershkrimi i shmbullit te

mesiperm eshte ky:secili cifte i anes semajte ne relacioni r eshte marre mesecilin cifte te anes se djathte ngarelacioni s

Kompozimi i operacioneveMe kombinimin e operacioneve te mesipermemund te behet krijimi i shprehjeve

i l h A C( )




operacionale,psh : A=C(r x s )r x s

A=C(r x s )

A B

1111

2 2

2 2

C D

1010

20101010

2010

E

aabbaa

bb

A B C D E

1 2 2

10 20 20

aab



Riemrimi i OperacioneveLejon emerim dhe me kete mund ti

i j lt ti t h hj




qasemi nje rezultati te shprehjesrelacionale algjebrike.

Lejon referim te nje relacioni me me

shume se nje emer.psh : x (E )Kjo na mundeson shikim e te dhenes nga

shprehja E me emrin X.

Nese shprehja algjebrike E ka nje gjatesin,atehere x (A1, A2, …, An ) (E )

Na jepe rezultatin e shprehjes E meemer X dhe me atribute e riemruaraA 1 , A2, …., An .

Shembuj te relacioneve

branch (branch name branch cit assets)




branch (branch-name, branch-city, assets)customer (customer-name, customer-street,

customer-only)

account (account-number, branch-name,balance)

loan (loan-number, branch-name, amount)

depositor (customer-name, account-number)

borrower (customer-name, loan-number)

Shembull i pyetsorit

Gj ni t jith h t m t m dh s




Gjeni te gjitha huate me te medha sesa $1200.kjo pershkohet me keterelacion

Gjeni numrin e huase per secilen hua me sasi me te

madhe se sa $1200

amount > 1200 (loan)

loan-number (amount > 1200 (loan))

Shembuj te metejme tepyetsoreve

Gjeni emrat e te gjithe klienteve




Gjeni emrat e te gjithe klienteve(―customer‖)te cilet kane hua, njellogari ose qe te dyja nga banka

Gjeni emrat e te gjithe klienteve te cilet kane hua dhenje llogari bankare.

customer-name (borrower ) customer-name (depositor )

customer-name (borrower ) customer-name (depositor )

Shembuj pyetsoresh (vazh)Gjeni emrat e te gjithe klienteve te cilet

kane hua ne filialllen ―Perryridge‖




kane hua ne filialllen Perryridge .

Gjeni emrat e te gjithe klienteve te cilet kane hua ne filiallen“ Perryridge” dhe te cilet nuk kane asnje llogari ne ndonje

filialle te bankes.

customer-name (branch-name = “Perryridge”

(borrower.loan-number = loan.loan-number (borrower x loan)))

–

customer-name(depositor)

customer-name (branch-name=“Perryridge”

( borrower.loan-number = loan.loan-number (borrower x loan)))



Shembuj pyetsoresh (vazh)

Gjeni llogarine e ballancuare me te




Gjeni llogarine e ballancuare me temadhe (account balance)Riemroje relacionine ellogarise si d

Zgjidhja :

balance

(account) - account.balance

(account.balance < d.balance (account x d

(account )))

Definimi formal i nje shprehjeNje shprehje relacionale ne algjeberrelacionale perbehet nga keto dy elemente

themelore :Relacioni eshte ne BDH(baze te te dhenave)




themelore :Relacioni eshte ne BDH(baze te te dhenave)Dhe nga nje relacion konstant

Le te jene E 1 dhe E 2 dy shprehje algjebrike

relacionale ; keto jane te gjitha shprehjetrelacionale algjebrike per to :

E 1 E 2

E 1 - E 2 E 1 x E 2 p (E 1 ), P eshte nj epredikat i atributeve ne E 1 s (E 1 ), S eshte nje liste e cila permbane disa ngaatributet e E 1 x (E 1 ), x eshte nje emer i ri per rezultatin e E 1-

Operacionet shtese

Ne mund te definojme operacione




Ne mund te definojme operacioneshtese te cilet nuk e bejne fuqizimine algjebres relacionale por bejne

thjeshtesin e pyetsoreve.Prerja e bashkesive(Set intersection)

Lidhja e bashkesive (Natural join)

Pjestimi (Division)

Ndarja (Assignment)

Prerja e bashkesive

Shenimi : r sD fi h t t l i it




Shenimi : r s Definohet me ane te relacionit:r s ={ t | t r dhe t s }

Supozojme se :r , s kane te njejten gjatesiatributet e r dhe s jane kompatibile

Ateher dihet matematikisht seA B =A\(A\B),keshtu mund temarrim se: r s = r - (r - s )

Prerja e bashkesive-shembullLe te jene dhene relacionet r, s:

A B

1

A B

2




Ateher me prerje r s marrim:

121

23

r s

A B

2

shenimi i ketij operacioni do te jete : r s Operacioni i lidhjes natyraleLe te jene r dhe s relacione ne skemat R dhe

S perkatesishtAt h ht l i k R S




S perkatesisht.Ateher r s eshte relacion nga skema R S e marre si me poshte:

Merret ne konsiderate secili cift t r

nga r dhe t s

nga s .Nese t r dhe t s kane te njejten vlere ne secilin ngaatributet ne R S , shtohet cifti t ne rezultat,ku

t ka vlere te njejte sikurse t

r ne r

t ka vlere te njejte sikurse t s ne s Psh :

R = (A, B, C, D )S = (E, B, D )

Skema e rezulatit = (A, B, C, D, E )r s eshte definuare sikurse :

r.A, r.B, r.C, r.D, s.E (r.B = s.B r.D = s.D (r x s ))

Operacioni i lidhjes natyrore

Me perkufizim te operacionit te




Me perkufizim te operacionit telidhjes natyrore shihet se kjorealizohet per dy relacionet eshqyrtuara R dhe S te marra ngaunioni i tyre ashtu qe rekordet eatributeve te cilat jane ne te dyshprehjet merren sipas produktitkartezian te tyre.kjo shihet mekete shembull

Shembull i lidhje natyroreJane dhene relacionet r, s:

A B C D B D E




A B

1 2

41

2

C D

aa

bab

B

13

1 23

D

aa

abb

E

r

A B

11

11

2

C D

aa

aab

E

sr s

Operacioni ipjestimit(division)

Le te jene r dhe s relacione ne skematR dhe S te dhena me

r s




Le te jene r dhe s relacione ne skematR dhe S te dhena me

R = (A 1, …, A m , B 1, …, B n )

S = (B 1, …, B n )Rezultati i shprehjes r s eshte nje relacion

ne skemen

R – S = (A 1, …, A m )Te definuare me shprehjen

r s = { t | t R-S (r ) u s ( tu

r ) }

Shembull i operacionit tepjestimit

Relacionet r, s: B

A B




r s: A

1

2

1 23

111346

1 2

r

s

Another Division Example

A B C D E

Relations r, s:D E




aaa

aaaaa

aab

ababb

111

13111

r s:

ab

11

A B

aa

C

r

s

Division Operation (Cont.)

PropertyLet q r s




p yLet q – r s Then q is the largest relation satisfyingq x s r

Definition in terms of the basicalgebra operationLet r(R) and s(S) be relations, and

let S R

r s = R-S (r ) –R-S ( (R-S (r ) x s )–

R-S,S (r ))

To see whyR-S,S (r ) simply reorders attributes of r

Assignment OperationThe assignment operation ()

provides a convenient way toexpress complex queries




p yexpress complex queries.Write query as a sequential programconsisting of

a series of assignmentsfollowed by an expression whose value isdisplayed as a result of the query.

Assignment must always be made to a

temporary relation variable.Example: Write r s as

temp 1 R-S (r )

temp 2 R-S ((temp 1 x s )– R-S,S (r ))

result = tem 1 – tem 2

Example Queries

Query 1




Find all customers who have an accountfrom at least the ―Downtown‖ and the

Uptown‖ branches.

where CN denotes customer-name and BN denotes

branch-name.

Query 1

CN(BN =“Downtown”(deposi tor account ))

CN (BN =“Uptown”(depositor account ))

Query 2

customer-name, branch-name (depositor account )

temp(branch-name ) ({(“Downtown”), (“Uptown”)})

Find all customers who have an account

at all branches located in Brooklyn

Example Queries




y

city.customer-name, branch-name (depositor

account )

branch-name (branch-city = “Brooklyn” (branch))

x en e e a ona -Algebra-Operations

G li d P j ti




Generalized Projection

Outer Join

Aggregate Functions

Generalized Projection




Extends the projection operation byallowing arithmetic functions to be

used in the projection list.

F1, F2, …, Fn(E )E is any relational-algebra expressionEach of F 1, F 2, …, F n are arearithmetic expressions involvingconstants and attributes in the

schema of E .Given relation credit-info(customer- name, limit, credit-balance), find howmuch more each erson can s end:

Aggregate unctions anOperations




Aggregation function takes acollection of values and returns a

single value as a result.avg: average valuemin: minimum valuemax: maximum valuesum: sum of valuescount: number of values

Aggregate operation in relational

algebraG1, G2, …, Gn g F1( A1), F2( A2),…, Fn( An)

(E )

Aggregate Operation – Example

l

A B C




Relation r :

7

7

310

g sum(c) (r)sum-C

27

Aggregate Operation – Example




Relation account grouped bybranch-name :

branch-name g sum(balance) (account )

branch-name account-number balance

PerryridgePerryridgeBrightonBrightonRedwood

A-102A-201A-217A-215A-222

400900750750700

branch-name balance

PerryridgeBrightonRedwood

13001500700

Aggregate Functions (Cont.)




Result of aggregation does nothave a name

Can use rename operation to give it aname

For convenience, we permit renamingas part of aggregate operation

branch-name g sum (balance) as sum-balance(account )

Outer Join

A t i f th j i ti




An extension of the join operationthat avoids loss of information.

Computes the join and then addstuples form one relation that does notmatch tuples in the other relation tothe result of the join.Uses null values:

null signifies that the value is unknown ordoes not exist

All comparisons involving null are (roughlyspeaking) false by definition.Will study precise meaning of comparisonswith nulls later

Outer Join – Example

loan-number amount branch-name




Relation loan

Relation borrower

customer-name loan-number JonesSmithHayes

L-170L-230L-155

30004000

1700

L-170L-230

L-260

DowntownRedwood

Perryridge





Inner Join

loan Borrower

loan-number amount

L-170

L-230

3000

4000

customer-name

Jones

Smith

branch-name

Downtown

Redwood

JonesSmithnull

loan-number amount

L-170L-230L-260

300040001700

customer-name branch-name

DowntownRedwoodPerryridge

Left Outer Join

loan Borrower


Right Outer Join

loan number amount customer namebranch name




Right Outer Joinloan borrower

loan borrower

Full Outer Join

loan-number amount

L-170L-230L-155

30004000null

customer-name

JonesSmithHayes

branch-name

DowntownRedwoodnull

loan-number amount

L-170L-230L-260

L-155

300040001700

null

customer-name

JonesSmithnull

Hayes

branch-name

DowntownRedwoodPerryridge

null

Null Values

It is possible for tuples to have a null




It is possible for tuples to have a nullvalue, denoted by null , for some of

their attributesnull signifies an unknown value or thata value does not exist.

The result of any arithmeticexpression involving null is null.Aggregate functions simply ignore nullvalues

Is an arbitrary decision. Could havereturned null as result instead.We follow the semantics of SQL in itshandling of null values

Null ValuesComparisons with null values return

the special truth value unknownIf false was used instead of unknown , thent (A 5)




not (A < 5) would not be equivalent to

A >= 5Three-valued logic using the truthvalue unknown :

OR: (unknown or true ) = true ,

(unknown or false ) = unknown (unknown or unknown) = unknown

AND: (true and unknown) = unknown,(false and unknown) = false,

(unknown and unknown) = unknownNOT : ( not unknown) = unknownIn SQL ―P is unknown” evaluates to true ifpredicate P evaluates to unknown

Modification of the Database

The content of the database may




The content of the database maybe modified using the following

operations:DeletionInsertion

UpdatingAll these operations areexpressed using the assignment

operator.

Deletion

A delete request is expressed




A delete request is expressedsimilarly to a query, except instead of

displaying tuples to the user, theselected tuples are removed from thedatabase.Can delete only whole tuples; cannotdelete values on only particularattributesA deletion is expressed in relational

algebra by:r r – E

where r is a relation and E is a

Deletion ExamplesDelete all account records in thePerryridge branch.account account – branch-name = “Perryridge” (account)




Delete all accounts at branches located in Needham.

r 1 branch-city = “Needham” (account branch)

r 2 branch-name, account-number, balance (r 1)

r 3 customer-name, account-number (r 2 depositor)

account account – r 2

depositor depositor – r 3

Delete all loan records with amount in the range of 0 to 50

loan loan – amount 0 and amount 50 (loan)

Insertion

To insert data into a relation we




To insert data into a relation, weeither:

specify a tuple to be insertedwrite a query whose result is a set oftuples to be inserted

in relational algebra, an insertion isexpressed by:

r r E where r is a relation and E is a

relational algebra expression.The insertion of a single tuple isexpressed by letting E be a constant

i i i

Insertion Examples

Insert information in the databaseaccount account {(“Perryridge”, A-973, 1200)}




Insert information in the databasespecifying that Smith has $1200 in

account A-973 at the Perryridgebranch. Provide as a gift for all loan customers in thePerryridge

branch, a $200 savings account. Let the loan number

serveas the account number for the new savings account.

depositor depositor {(“Smith”, A-973)}

r 1 (branch-name = “Perryridge” (borr ower loan ))

account account branch-name, account-number,200 (r 1)

depositor depositor customer-name, loan-number (r 1)



ViewsIn some cases, it is not desirable for

all users to see the entire logical model(i.e., all the actual relations stored inthe database.)




the database.)Consider a person who needs to know a

customer‘s loan number but has noneed to see the loan amount. Thisperson should see a relation described,in the relational algebra, bycustomer-name, loan-number (borrowerloan )Any relation that is not of the

conceptual model but is made visible toa user as a ―virtual relation‖ is called aview.

View Definition

A view is defined using the create




gview statement which has the form

create view v as < query expressionwhere <query expression> is any legalrelational algebra query expression.

The view name is represented by v. Once a view is defined, the view namecan be used to refer to the virtual

relation that the view generates.View definition is not the same ascreating a new relation by evaluatingthe query expression

View Examples

Consider the view (named all- create view all-customer as

(d

it t)




(customer ) consisting of branches and

their customers.

We can find all customers of the Perryridge branch by writing:

branch-name, customer-name (depositor account)

branch-name, customer-name (borrower loan)

branch-name

(branch-name = “Perryridge” (all-customer ))

Updates Through View

Database modifications expressed as




pviews must be translated to

modifications of the actual relations inthe database.Consider the person who needs to seeall loan data in the loan relation exceptamount. The view given to the person,branch-loan, is defined as:

create view branch-loan as

branch-name, loan-number (loan) Since we allow a view name to appearwherever a relation name is allowed,

Updates Through Views(Cont.)The previous insertion must be

represented by an insertion into theactual relation loan from which the viewbranch-loan is constructed.




branch loan is constructed.An insertion into loan requires a valuefor amount . The insertion can be dealtwith by either.

rejecting the insertion and returning anerror message to the user.inserting a tuple (―L-37‖, ―Perryridge‖, null )into the loan relation

Some updates through views are

impossible to translate into databaserelation updatescreate view v as branch-name = ―Perryridge‖ (account ))

Views Defined Using OtherViews

One view may be used in thei d fi i h i




expression defining another view

A view relation v 1 is said to dependdirectly on a view relation v 2 if v 2 isused in the expression defining v 1

A view relation v 1 is said to depend on view relation v 2 if either v1 dependsdirectly to v 2 or there is a path ofdependencies from v1 to v2

A view relation v is said to berecursive if it depends on itself.

View Expansion

A way to define the meaning of viewsd fi d i t f th i




defined in terms of other views.

Let view v 1 be defined by anexpression e 1 that may itself containuses of view relations.View expansion of an expressionrepeats the following replacementstep:repeat

Find any view relation v i in e 1 Replace the view relation v i by theexpression defining v i until no more view relations are

Tuple Relational CalculusA nonprocedural query language, where

each query is of the form{t | P (t ) }It is the set of all tuples t such that




It is the set of all tuples t such thatpredicate P is true for tt is a tuple variable , t [A ] denotes thevalue of tuple t on attribute A t r denotes that tuple t is in relation r P is a formula similar to that of thepredicate calculus

Predicate Calculus Formula

1. Set of attributes and constants




2. Set of comparison operators: (e.g., ,

, , , , )3. Set of connectives: and (), or (v)‚

not ()

4. Implication (): x y, if x if true,then y is truex y x v y

5. Set of quantifiers: t r (Q(t)) ‖there exists‖ a tuple in t

in relation r such that predicate Q(t) is

true

Banking Example

branch (branch-name, branch-city,assets)




assets)

customer (customer-name, customer- street, customer-city)account (account-number, branch- name, balance)loan (loan-number, branch-name,amount)depositor (customer-name, account-

number)borrower (customer-name, loan- number)

Example Queries

Find the loan-number, branch-name,and amount for loans of over $1200

{t | t loan t [amount ] 1200}




and amount for loans of over $1200Find the loan number for each loan of an amount greater than

$1200

Notice that a relation on schema [loan-number ] is implicitlydefined by the query

{t | s loan (t [loan-number ] = s[loan-number ] s [amount ] 1200)}

Example Queries

Find the names of all customers havinga loan an account or both at the bank{t | s borrower( t [customer-name] = s[customer-name])

u depositor ( t [customer-name] = u[customer-name])




a loan, an account, or both at the bank

{t | s borrower( t [customer-name] = s[customer-name])

u depositor ( t [customer-name] = u[customer-name])

Find the names of all customers who have a loan and anaccount

at the bank

p ( [ ] [ ])

Example Queries

Find the names of all customers havinga loan at the Perryridge branch

{t | s borrower(t [customer-name] = s[customer-name] u loan(u[branch-name] = “Perryridge”




a loan at the Perryridge branch

{t | s borrower( t [customer-name] = s[customer-name] u loan(u[branch-name] = “Perryridge”

u[loan-number ] = s[loan-number ])) not v depositor (v [customer-name] =

t [customer-name]) }

Find the names of all customers who have a loan at thePerryridge branch, but no account at any branch of the bank

u[loan-number ] = s[loan-number ]))}

Example Queries

Find the names of all customers havinga loan from the Perryridge branch

{t | s loan(s[branch-name] = “Perryridge” u borrower (u[loan-number ] = s[loan-number ]




a loan from the Perryridge branch,

and the cities they live in

( [ ] [ ] t [customer-name] = u[customer-name])

v customer (u[customer-name] = v [customer-name] t [customer-city ] = v [customer-city ])

Example Queries

Find the names of all customers whohave an account at all branches

{t | c customer (t [customer.name] = c[customer-name])

s branch(s[branch-city] = “Brooklyn”




have an account at all branches

located in Brooklyn:

s branch(s[branch-city ] = Brooklyn u account ( s[branch-name] = u[branch-name]

s depositor ( t [customer-name] = s[customer-name s[account-number ] = u[account-number] )) )

Safety of Expressions

It is possible to write tuple calculusexpressions that generate infinite




expressions that generate infinite

relations.For example, {t | t r } results in aninfinite relation if the domain of anyattribute of relation r is infinite

To guard against the problem, werestrict the set of allowableexpressions to safe expressions.

An expression {t | P (t )} in the tuplerelational calculus is safe if everycomponent of t appears in one of therelations, tu les, or constants that



Example QueriesFind the loan-number, branch-name, and

amount for loans of over $1200

Find the names of all customers who have a loan of over $1200

{ l , b, a | l , b, a loan a > 1200}




{ c, a | l ( c, l borrower b( l, b, a loan

b = “Perryridge”))}

or { c, a | l ( c, l borrower l, “ Perryridge”, a loan)}

Find the names of all customers who have a loan from thePerryridge branch and the loan amount:

{ c | l, b, a ( c, l borrower l, b, a loan a > 12

Find the names of all customers who have a loan of over $1200

Example Queries

Find the names of all customers havinga loan, an account, or both at the

{ c | l ({ c, l borrower b,a( l, b, a loan b = “Perryridge”))

a( c a depositor




a loan, an account, or both at the

Perryridge branch:

{ c | s, n ( c, s, n customer)

x,y,z ( x, y, z branch y = “Brooklyn”) a,b( x, y, z account c,a depositor )}

Find the names of all customers who have an account atall

branches located in Brooklyn:

a( c, a depositor

b,n( a, b, n account b = “Perryridge”))}

Safety of Expressions

{ x 1, x 2, …, x n | P (x 1, x 2, …, x n )}




is safe if all of the following hold:1.All values that appear in tuples ofthe expression are values fromdom (P ) (that is, the values appeareither in P or in a tuple of a relationmentioned in P ).2.For every ―there exists‖ subformula

of the form x (P 1(x )), thesubformula is true if an only if P 1(x ) istrue for all values x from dom (P 1).

― ‖

End of Chapter 3




p

esu o branch-name =

―Perryridge‖ (loan )




of the Loan




ames o ustomersWho Have Either a Loan oran Account




But No Loan




Result of borrower loan




Result of branch-name = ―Perryridge‖

(borrower loan)




Result of customer-name




Result of the Subexpression




Largest Account Balance inthe Bank



Customers With Both anAccount and a Loan at theBank




Result of customer-name, loan-

number, amount (borrower loan)




ranc -

name ( customer-city =

―Harrison‖(customer account

depositor))




Result of branch-name ( branch-city =―Brooklyn‖(branch))




esu t o customer-name, branch-

name (depositor account)




The credit-info Relation




Result of customer-name, (limit – credit-balance) as credit-

available (credit-info).



-

After Grouping




ranc -name sum sa ary

(pt-works)




Result of branch-name sum salary,max(salary ) as max-salary (pt-works)




The employee and ft-worksRelations




The Result of employee ft- works




The Result of employee ft-works




Result of employee ft- works




Tuples Inserted Into loan andborrower



nbraha-bazat e te dhenave 187 ames o us omers

Who Have a Loan at thePerryridge Branch




E-R Diagram




The branch Relation




The loan Relation




The borrower Relation




Chapter 4: SQL

Basic StructureSet Operations

A t F ti




Aggregate FunctionsNull ValuesNested Subqueries

Derived RelationsViewsModification of the Database

Joined RelationsData Definition LanguageEmbedded S L, ODBC and JDBC

Schema Used in Examples




Basic StructureSQL is based on set and relational

operations with certain modificationsand enhancementsA typical SQL query has the form:

select A 1, A 2, ..., A n

from r1 r2 rm




from r 1, r 2, ..., r m where P A i s represent attributesr

i

s represent relationsP is a predicate.

This query is equivalent to therelational algebra expression.

A 1, A2, ..., An (P (r 1 x r 2 x ...x r m ))

The select ClauseThe select clause list the attributesdesired in the result of a query

corresponds to the projection operation ofthe relational algebra

E.g. find the names of all branches in

the loan relationl t b h




the loan relationselect branch-name from loan

In the ―pure‖ relational algebra syntax,

the query would be:branch-name(loan)

NOTE: SQL does not permit the ‗-‘

character in names,Use, e.g., branch_name instead of branch- name in a real implementation.

‗ ‘

The select Clause (Cont.)

SQL allows duplicates in relations aswell as in query results.To force the elimination of duplicates,insert the keyword distinct after




insert the keyword distinct afterselect.Find the names of all branches in the

loan relations, and remove duplicatesselect distinct branch-name from loan

The keyword all specifies thatduplicates not be removed.select all branch-name



The where Clause

The where clause specifies conditionsthat the result must satisfy

corresponds to the selection predicate of

the relational algebra




the relational algebra.To find all loan number for loans madeat the Perryridge branch with loan

amounts greater than $1200.select loan-numberfrom loanwhere branch- name = ‗ Perryridge‘

and amount > 1200Comparison results can be combinedusing the logical connectives and, or,

The where Clause (Cont.)SQL includes a between comparisonoperatorE.g. Find the loan number of thoseloans with loan amounts between$90,000 and $100,000 (that is,

$90 000 and $100 000)

select loan-number from loan

where amount between 90000 and 100000




$90,000 and $100,000) 90000 00000

The from ClauseThe from clause lists the relations involvedin the query

corresponds to the Cartesian product operationof the relational algebra.

Find the Cartesian product borrower x loan

select from borrower loan




select from borrower, loan Find the name, loan number and loan amount of allcustomers

having a loan at the Perryridge branch.

select customer-name, borrower.loan-number, amountfrom borrower, loanwhere borrower.loan-number = loan.loan-number and

branch-name = „Perryridge‟

The Rename OperationThe SQL allows renaming relations andattributes using the as clause:

old-name as new-name

Find the name, loan number and loanamount of all customers; rename the




amount of all customers; rename thecolumn name loan-number as loan-id. select customer-name, borrower.loan-number as loan-id,amountfrom borrower, loan

where borrower.loan-number = loan.loan-number

Tuple Variables

Tuple variables are defined in thefrom clause via the use of the asclause.

Find the customer names and their

select customer-name, T.loan-number, S.amountfrom borrower as T, loan as S

where T.loan-number = S.loan-number




Find the customer names and theirloan numbers for all customers havinga loan at some branch.

select distinct T.branch-namefrom branch as T, branch as Swhere T.assets > S.assets and S.branch-city = „ Brooklyn‟

Find the names of all branches that have greaterassets than

some branch located in Brooklyn.

String OperationsSQL includes a string-matchingoperator for comparisons on character

strings. Patterns are described usingtwo special characters:

percent (%). The % character matches anysubstring.underscore ( ). The character matches




underscore (_). The _ character matchesany character.

Find the names of all customers whose

street includes the substring ―Main‖. select customer-namefrom customerwhere customer-street like

‘%Main%’

Match the name ―Main%‖ ‘ ’ ‘ ’

Ordering the Display ofTuples

List in alphabetic order the names ofall customers having a loan inPerryridge branch

select distinct customer-name




select distinct customer namefrom borrower, loanwhere borrower loan-number -

loan.loan-number andbranch-name = ‘Perryridge’ order by customer-name

We may specify desc for descending

order or asc for ascending order, foreach attribute; ascending order is thedefault.

Duplicates

In relations with duplicates, SQL candefine how many copies of tuplesappear in the result.

Multiset versions of some of the




Mu t s t versions of some of therelational algebra operators – givenmultiset relations r 1 and r 2:

1. (r 1 ): If there are c 1 copies of tuple t 1 in r 1, and t 1 satisfies selections ,, thenthere are c 1 copies of t 1 in (r 1).

2.A (r) : For each copy of tuple t

1 in r

1,

there is a copy of tuple A (t 1) in A (r 1) where A (t 1) denotes the projection ofthe single tuple t 1 .

Duplicates (Cont.)Example: Suppose multisetrelations r 1 (A, B ) and r 2 (C ) are as

follows:r 1 = {(1, a ) (2,a )} r 2 = {(2),

(3), (3)}

Then B (r 1) would be {(a), (a)},while B(r1) x r2 would be




hen ( ) would be {(a), (a)},while B (r 1) x r 2 would be{(a ,2), (a ,2), (a ,3), (a ,3), (a ,3),

(a ,3)}SQL duplicate semantics:

select A 1,, A 2, ..., A n from r 1, r 2, ..., r m where P

is equivalent to the multiset version of the ex ression:

Set Operations

The set operations union, intersect,and except operate on relations andcorrespond to the relational algebra

operations




p Each of the above operationsautomatically eliminates duplicates; to

retain all duplicates use thecorresponding multiset versions unionall, intersect all and except all.

Suppose a tuple occurs m times in r and n times in s, then, it occurs:m + n times in r union all s

Set Operations

Find all customers who have a loan, anaccount, or both:

(select customer-name from depositor )intersect

(select customer-name from depositor )

union(select customer-name from borrower)

Find all customers who have both a loan and an account.




(select customer-name from depositor )except(select customer-name from borrower)

intersect(select customer-name from borrower)

Find all customers who have an account but no loan.

Aggregate Functions

These functions operate on themultiset of values of a column of a

relation, and return a valuel




n, n u n uavg: average valuemin: minimum value

max: maximum valuesum: sum of valuescount: number of values

Aggregate Functions (Cont.)

Find the average account balance atthe Perryridge branch.

Find the number of tuples in the customer relation.

select avg (balance) from accountwhere branch-name = „Perryridge‟

select count (*)




Find the number of depositors in the bank.

from customer

select count (distinct customer-name)from depositor

Aggregate Functions – GroupBy

Find the number of depositors for eachbranch.select branch-name, count (distinct customer-name)

from depositor, accountwhere depositor.account-number = account.account-nu

group by branch-name




Note: Attributes in select clause outside of aggregatefunctions must

appear in group by list

ggrega e unc on –

Having Clause

Find the names of all branches wherethe average account balance is morethan $1,200.

N di i h h i l li d f h

select branch-name, avg (balance)from accountgroup by branch-namehaving avg (balance) > 1200




Note: predicates in the having clause are applied after theformation of groups whereas predicates in the

where

clause are applied before forming groups

Null ValuesIt is possible for tuples to have a nullvalue, denoted by null , for some of

their attributesnull signifies an unknown value or thata value does not exist.

The predicate is null can be used tocheck for null values.




f u u .E.g. Find all loan number which appear inthe loan relation with null values for

amount. select loan-numberfrom loanwhere amount is null

The result of any arithmeticexpression involving null is null

u a ues an T ree

Valued Logic

Any comparison with null returnsunknown

E.g. 5 < null or null <> null or null =

nullThree valued logic using the truth




Three-valued logic using the truthvalue unknown :

OR: (unknown or true ) = true , (unknown or false ) = unknown

(unknown or unknown) = unknownAND: (true and unknown) = unknown,(false and unknown) = false,

(unknown and unknown) = unknownNOT : ( not unknown) = unknown―P is unknown” evaluates to true if

Null Values and Aggregates

Total all loan amounts

select sum (amount)

from loan Above statement ignores null amounts




g

result is null if there is no non-null amount,that is the

All aggregate operations exceptcount(*) ignore tuples with null valueson the aggregated attributes.

Nested Subqueries

SQL provides a mechanism forthe nesting of subqueries.

A subquery is a select-from-where expression that is nested




pwithin another query.

A common use of subqueries is toperform tests for setmembership, set comparisons, andset cardinality.

Example Query

Find all customers who have both anaccount and a loan at the bank.

Find all customers who have a loan at the bank but do

select distinct customer-namefrom borrowerwhere customer-name in (select customer-name

from depositor)




Find all customers who have a loan at the bank but donot have

an account at the bank

select distinct customer-namefrom borrowerwhere customer-name not in (select customer-name

from depositor)

Example Query

Find all customers who have both anaccount and a loan at the Perryridgebranch

select distinct customer-namefrom borrower, loanwhere borrower.loan-number = loan.loan-number and

branch-name = “Perryridge” and

(branch-name, customer-name) in(select branch-name, customer-name




Note: Above query can be written in a much simplermanner. The

formulation above is simply to illustrate SQL features.(Schema used in this example)

from depositor, accountwhere depositor.account-number =

account.account-number)

Set Comparison

Find all branches that have greaterassets than some branch located inBrooklyn.

Same query using > some clause

select distinct T.branch-namefrom branch as T, branch as Swhere T.assets > S.assets and

S.branch-city =‘Brooklyn

’




select branch-namefrom branch

where assets > some(select assetsfrom branch

where branch-city = ‘Brooklyn’)

Definition of Some Clause

F <comp> some r t r s.t.( F <comp> t ) Where <comp> can be:

0

5

6

(5<some

) =true

05 ) = false

(read: 5 < some tuple in the relation)

(5<




05

05(5 some ) = true (since 0 5)

some

) = true(5 = some

(= some) in

However, ( some) not in

Definition of all Clause

F <comp> all r t r (F<comp> t)

0

5

6

(5< all ) = false

610 ) = true(5< all




45

46(5 all ) = true (since 5 4 and 5 6)

) = false(5 = all

( all) not in

However, (= all) in

Example Query

Find the names of all branches thathave greater assets than all brancheslocated in Brooklyn.

select branch-namefrom branchwhere assets > all

(select assets

from branchwhere branch-city = „Brooklyn‟)




Test for Empty Relations

The exists construct returns thevalue true if the argument

subquery is nonempty.exists r r Ø




not exists r r = Ø

Example Query

Find all customers who have an accountat all branches located in Brooklyn.

select distinct S.customer-namefrom depositor as Swhere not exists (

(select branch-namefrom branch

where branch-city = „Brooklyn‟) except

(select R.branch-name




(from depositor as T, account as Rwhere T.account-number = R.account-number and

S.customer-name = T.customer-name))

(Schema used in this example)

Note that X – Y = Ø X Y

Note: Cannot write this query using = all and its variants



Example Query

Find all customers who have at leasttwo accounts at the Perryridgebranch.

select distinct T.customer-namefrom depositor Twhere not unique (

select R.customer-name

from account, depositor as Rwhere T.customer-name = R.customer-name

and




andR.account-number = account.account-number

and

account.branch-name = ‘Perryridge’)

(Schema used in this example)



Example QueriesA view consisting of branches and theircustomers

create view all-customer as

(select branch-name, customer-namefrom depositor, accountwhere depositor.account-number = account.account-number

union(select branch-name, customer-namefrom borrower, loanwhere borrower.loan-number = loan.loan-number)




Find all customers of the Perryridge branch

select customer-namefrom all-customerwhere branch-name = „Perryridge‟

Derived Relations

Find the average account balance ofthose branches where the averageaccount balance is greater than $1200.

select branch-name, avg-balancefrom (select branch-name, avg

(b l )




(balance)from accountgroup by branch-name)as result (branch-name, avg-

balance)

where avg-balance > 1200Note that we do not need to use thehaving clause, since we compute the

With Clause

With clause allows views to be definedlocally to a query, rather than globally.Analogous to procedures in a

programming language.Find all accounts with the maximumb l




balance

with max-balance (value ) as select max (balance )from account

select account-numberfrom account, max-balancewhere account.balance = max-

Complex Query using WithClause

Find all branches where the totalaccount deposit is greater than theaverage of the total account deposits

at all branches.

with branch-total (branch-name, value) as select branch-name, sum (balance)from account group by branch-name

with branch-total -avg(value) as select avg (value)from branch-total




from branch-total select branch-name from branch-total , branch-total-avgwhere branch-total.value >= branch-total-avg.value

o ca on o e

Database – DeletionDelete all account records at thePerryridge branch

delete from accountwhere branch-name =‘Perryridge’

Delete all accounts at every branch

located in Needham city.delete from accounth b h ( l b h




where branch-name in (select branch-

name from branchwhere branch-city =

‘Needham’)

delete from depositorwhere account-number in(select account-

Example Query

Delete the record of all accounts withbalances below the average at thebank.

delete from accountwhere balance < (select avg (balance)

from account)

Problem: as we delete tuples from deposit, the average balancechanges




Solution used in SQL:

1. First, compute avg balance and find all tuples to delete

2. Next, delete all tuples found above (without recomputing avg orretesting the tuples)

o ca on o e

Database – Insertion

Add a new tuple to accountinsert into account

values (‗A-9732‘,

‗Perryridge‘,1200) or equivalently




insert into account (branch-name,balance, account-number)

values (‗Perryridge‘, 1200, ‗A-9732‘)

Add a new tuple to account withbalance set to nullinsert into account

o ca on o e

Database – InsertionProvide as a gift for all loan customersof the Perryridge branch, a $200

savings account. Let the loan numberserve as the account number for thenew savings account

insert into accountselect loan-number, branch-name,

200f l




from loan

where branch-name = ‗Perryridge‘ insert into depositorselect customer-name, loan-numberfrom loan, borrower

where branch-name = ‗ Perryridge‘ and loan.account-number =borrower.account-number



Case Statement for

Conditional Updates

Same query as before: Increase allaccounts with balances over $10,000by 6%, all other accounts receive 5%.

update account set balance = case




set balance = case when balance <=

10000 then balance *1.05else balance *

1.06

end

Update of a ViewCreate a view of all loan data in loan relation, hiding the amount attribute

create view branch-loan asselect branch-name, loan- number

from loan

Add a new tuple to branch-loaninsert into branch-loan

l (‗P id ‘ ‗L 307‘)




values (‗Perryridge‘, ‗L-307‘)

This insertion must be represented bythe insertion of the tuple(‗L-307‘, ‗Perryridge‘, null )

into the loan relationUpdates on more complex views aredifficult or impossible to translate,

TransactionsA transaction is a sequence of queriesand update statements executed as a

single unitTransactions are started implicitly andterminated by one of

commit work: makes all updates of the

transaction permanent in the database rollback work: undoes all updates performed bythe transaction.

M i i l




Motivating example

Transfer of money from one account toanother involves two steps:deduct from one account and credit to another

If one steps succeeds and the other fails,

database is in an inconsistent stateTherefore, either both steps should succeedor neither should

Transactions (Cont.)

In most database systems, each SQLstatement that executes successfullyis automatically committed.

Each transaction would then consist ofonly a single statementAutomatic commit can usually be turned




yoff, allowing multi-statement

transactions, but how to do so depends onthe database systemAnother option in SQL:1999: enclosestatements within

begin atomic…end

Joined Relations

Join operations take two relations andreturn as a result another relation.These additional operations are

typically used as subquery expressionsin the from clauseJoin condition – defines which tuples




Join condition – defines which tuples

in the two relations match, and whatattributes are present in the result ofthe join.Join type – defines how tuples in each

relation that do not match any tuple inthe other relation (based on the joincondition are treated.

Join Typesinner joinleft outer joinright outer joinfull outer join

Join Conditionsnaturalon <predicate>using ( A1, A2, ..., An)

o ne e a ons – a ase s

for ExamplesRelation loan

Relation borrower

customer-name loan-number

amount

3000

4000

1700

branch-name

Downtown

Redwood

Perryridge

loan-number

L-170L-230

L-260




Jones

SmithHayes

L-170

L-230L-155

Note: borrower information missing for L-260 andloan information missing for L-155

Joined Relations – Examples

loan inner join borrower onloan.loan-number =borrower.loan-number

loan left outer join borrower on loan.loan-number = borrower.loan-number

branch-name amount

Downtown

Redwood

3000

4000


Jones

Smith

L-170

L-230

loan-number

L-170

L-230




branch-name amount

Downtown

Redwood

Perryridge

3000

4000

1700


Jones

Smith

null

L-170

L-230

null

loan-number

L-170

L-230

L-260

Joined Relations – Examples

loan natural inner join borrower

loan natural right outer join borrower

branch-name amount

Downtown

Redwood

3000

4000

customer-name

Jones

Smith

loan-number

L-170

L-230




branch-name amount

Downtown

Redwood

null

3000

4000

null

customer-name

Jones

Smith

Hayes

loan-number

L-170

L-230

L-155

Joined Relations – Examplesloan full outer join borrowerusing (loan-number)

Find all customers who have either an account or a loan(b t t b th) t th b k

branch-name amount

Downtown

Redwood

Perryridge

null

3000

4000

1700

null

customer-name

Jones

Smith

null

Hayes

loan-number

L-170

L-230

L-260

L-155




(but not both) at the bank.

select customer-name from (depositor natural full outer join borrower ) where account-number is null or loan-number is nul

Data Definition Language(DDL)

The schema for each relation.The domain of values associatedwith each attribute.

Allows the specification of not only a set of relations but

also information about each relation, including:




Integrity constraintsThe set of indices to bemaintained for each relations.Security and authorization

information for each relation.The physical storage structure

Domain Types in SQLchar(n). Fixed length character string,with user-specified length n.

varchar(n). Variable length characterstrings, with user-specified maximumlength n.

int. Integer (a finite subset of theintegers that is machine-dependent).smallint. Small integer (a machine-d d t b t f th i t d i




dependent subset of the integer domain

type).numeric(p,d). Fixed point number, withuser-specified precision of p digits, withn digits to the right of decimal point.real, double precision. Floating pointand double-precision floating point

Date/Time Types in SQL(Cont.)

date. Dates, containing a (4 digit) year, month and date

E.g. date ‗2001-7-27‘

time. Time of day, in hours, minutesand seconds.E.g. time ‘09:00:30‘ time




g‘09:00:30.75‘

timestamp: date plus time of dayE.g. timestamp ‗2001-7-27 09:00:30.75‘

Interval: period of time

E.g. Interval ‗1‘ day Subtracting a date/time/timestamp valuefrom another gives an interval value

Create Table Construct

An SQL relation is defined usingthe create table command:

create table r (A 1 D 1, A 2 D 2, ..., A n D n ,

(integrity-constraint1),




1),...,(integrity-

constraintk))r is the name of the relation

each A i is an attribute name in theschema of relation rD i is the data type of values in the

Integrity Constraints inCreate Tablenot nullprimary key (A 1, ..., A n )

check (P), where P is a predicateExample: Declare branch-name as the primary keyfor branch and ensure that the values of assets arenon-negative.

create table branch(branch-namechar(15),branch-city char(30)assets integer




assets integer,primary key (branch-name),

check (assets >= 0))

primary key declaration on an attribute

automatically ensures not null in SQL-92onwards, needs to be explicitly stated in SQL-89

Drop and Alter TableConstructsThe drop table command deletes allinformation about the dropped

relation from the database.The alter table command is used toadd attributes to an existingrelation.

alter table r add A D

where A is the name of thett ib t t b dd d t l ti




attribute to be added to relation r

and D is the domain of A. All tuples in the relation are assignednull as the value for the new attribute.

The alter table command can also beused to drop attributes of a relationalter table r drop A

Embedded SQL

The SQL standard definesembeddings of SQL in a variety ofprogramming languages such as Pascal,

PL/I, Fortran, C, and Cobol.A language to which SQL queries areembedded is referred to as a hostl d th SQL t t




language, and the SQL structures

permitted in the host languagecomprise embedded SQL.The basic form of these languages

follows that of the System Rembedding of SQL into PL/I.EXEC S L statement is used to

Example Query

Specify the query in SQL and declare acursor for it

EXEC SQLdeclare c cursor forselect customer-name customer-city

From within a host language, find the names and citiesof customers with more than the variable amount dollars

in some account.




select customer name, customer city

from depositor, customer, accountwhere depositor.customer-name =customer.customer-name

and depositor account-number =

account.account-numberand account.balance > :amount

Embedded SQL (Cont.)

The open statement causes the queryto be evaluatedEXEC SQL open c END-EXEC

The fetch statement causes thevalues of one tuple in the query resultto be placed on host language

i bl




variables.EXEC SQL fetch c into :cn, :cc END-EXECRepeated calls to fetch get successive

tuples in the query resultA variable called SQLSTATE in the

Updates Through Cursors Can update tuples fetched by cursor by declaring that the

cursor is for update

declare c cursor forselect *from accountwhere branch-name = „Perryridge‟

for update

To update tuple at the current location of cursor

update accountset balance = balance + 100

h t f




where current of c

Dynamic SQLAllows programs to construct andsubmit SQL queries at run time.

Example of the use of dynamic SQLfrom within a C program.

char * sqlprog = ― update accountset balance =balance * 1.05

where account-number =




?‖ EXEC SQL prepare dynprog from:sqlprog;char account [10] = ―A-101‖;

EXEC SQL execute dynprog using:account;

ODBC

Open DataBase Connectivity(ODBC)standard

standard for application program to

communicate with a database server.application program interface (API) to

open a connection with a database,

d d d




send queries and updates,

get back results.

Applications such as GUI,spreadsheets, etc. can use ODBC

ODBC (Cont.)Each database system supportingODBC provides a "driver" library thatmust be linked with the client program.When client program makes an ODBCAPI call, the code in the librarycommunicates with the server to carry

out the requested action, and fetchresults.ODBC program first allocates an SQLn i nm nt th n d t b s




environment, then a databaseconnection handle.Opens database connection usingSQLConnect(). Parameters for

SQLConnect:connection handle,the server to which to connect

ODBC Codeint ODBCexample(){

RETCODE error;

HENV env; /* environment */HDBC conn; /* database connection */SQLAllocEnv(&env);SQLAllocConnect(env, &conn);SQLConnect(conn, "aura.bell-labs.com",SQL_NTS, "avi", SQL_NTS, "avipasswd",SQL_NTS);{ D t l k }




{ …. Do actual work … }

SQLDisconnect(conn);SQLFreeConnect(conn);

SQLFreeEnv(env);}

ODBC Code (Cont.)Program sends SQL commands to thedatabase by using SQLExecDirect

Result tuples are fetched usingSQLFetch()SQLBindCol() binds C language variablesto attributes of the query result

When a tuple is fetched, its attribute values areautomatically stored in corresponding C variables.Arguments to SQLBindCol()

ODBC stmt variable, attribute position in query result




ODBC stmt variable, attribute position in query result

The type conversion from SQL to C.The address of the variable.For variable-length types like character arrays,

The maximum length of the variableLocation to store actual length when a tuple is fetched.Note: A negative value returned for the length fieldindicates null value

Good programming requires checking



More ODBC FeaturesPrepared Statement

SQL statement prepared: compiled at thedatabase

Can have placeholders: E.g. insert intoaccount values(?,?,?)Repeatedly executed with actual values for theplaceholders

Metadata featuresfinding all the relations in the database andfinding the names and types of columns of a

lt l ti i th d t b




query result or a relation in the database.

By default, each SQL statement istreated as a separate transaction thatis committed automatically.

Can turn off automatic commit on a connectionSQLSetConnectOption(conn,SQL_AUTOCOMMIT, 0)}

ODBC Conformance Levels

Conformance levels specify subsets ofthe functionality defined by thestandard.

CoreLevel 1 requires support for metadataqueryingLevel 2 requires ability to send and




y

retrieve arrays of parameter values andmore detailed catalog information.

SQL Call Level Interface (CLI)standard similar to ODBC interface,

but with some minor differences.

JDBC

JDBC is a Java API for communicatingwith database systems supportingSQL

JDBC supports a variety of featuresfor querying and updating data, andfor retrieving query resultsJDBC also supports metadata




JDBC also supports metadataretrieval, such as querying aboutrelations present in the database andthe names and types of relation

attributesModel for communicating with thedatabase:



JDBC Code (Cont.)Update to databasetry {

stmt.executeUpdate( "insert into accountvalues('A-9732',

'Perryridge', 1200)");} catch (SQLException sqle) {

System.out.println("Could not insert tuple. "+ sqle);

}




Execute query and fetch and printresultsResultSet rset = stmt.executeQuery( "select

branch_name, avg(balance)

fromaccountgroup by

JDBC Code Details

Getting result fields:rs.getString(―branchname‖) andrs.getString(1) equivalent if

branchname is the first argument ofselect result.

Dealing with Null values




gint a = rs.getInt(―a‖); if (rs.wasNull())

Systems.out.println(―Got null value‖);

Prepared StatementPrepared statement allows queries to becompiled and executed multiple times

with different argumentsPreparedStatement pStmt =conn.prepareStatement(

―insert into

account values(?,?,?)‖); pStmt.setString(1,"A-9732");pStmt.setString(2, "Perryridge");pStmt.setInt(3, 1200);




pStmt.executeUpdate();

pStmt.setString(1, "A-9733");pStmt.executeUpdate();

Beware: If value to be stored indatabase contains a single quote or

Other SQL FeaturesSQL sessionsclient connects to an SQL server,establishing a sessionexecutes a series of statementsdisconnects the sessioncan commit or rollback the work

carried out in the sessionAn SQL environment containsseveral components, including auser identifier, and a schema,




which identifies which of severalschemas a session is using.

Sc emas, Cata ogs, an

Environments

Three-level hierarchy for namingrelations.

Database contains multiple catalogs

each catalog can contain multiple schemas SQL objects such as relations and viewsare contained within a schema

e.g. catalog5.bank-schema.account




Each user has a default catalog andschema, and the combination is uniqueto the user.

Default catalog and schema are set upfor a connection



Extra Material on JDBC

and ApplicationArchitectures




Transactions in JDBC

As with ODBC, each statement getscommitted automatically in JDBC

To turn off auto commit use

conn.setAutoCommit(false); To commit or abort transactions use

conn.commit() or




conn.rollback()To turn auto commit on again, use

conn.setAutoCommit(true);

Procedure and Function Callsin JDBCJDBC provides a class

CallableStatement which allows SQLstored procedures/functions to beinvoked.

CallableStatement cs1 =conn.prepareCall( ―{call proc (?,?)}‖ ) ;

CallableStatement cs2 =




conn.prepareCall( ―{? = call func(?,?)}‖ );

Result Set MetaData

The class ResultSetMetaDataprovides information about all thecolumns of the ResultSet.

Instance of this class is obtained bygetMetaData( ) function of ResultSet.Provides Functions for getting numberof columns, column name, type,




precision, scale, table from which thecolumn is derived etc.

ResultSetMetaData rsmd =

rs.getMetaData ( );for ( int i = 1; i <=++

Database Meta DataThe class DatabaseMetaData providesinformation about database relations

Has functions for getting all tables, allcolumns of the table, primary keys etc.E.g. to print column names and types of arelation

DatabaseMetaData dbmd =conn.getMetaData( );

ResultSet rs = dbmd.getColumns( null,




―BANK-DB‖, ―account‖, ―%‖ ); //Arguments: catalog, schema-pattern, table-pattern, column-pattern

// Returns: 1 row for each

column, with several attributes such as// COLUMN_NAME,

Application Architectures

Applications can be built using oneof two architectures

Two tier model

Application program running at usersite directly uses JDBC/ODBC tocommunicate with the database

Three tier model




Users/programs running at user sitescommunicate with an application server.The application server in turncommunicates with the database

Two-tier Model

E.g. Java code runs at client site anduses JDBC to communicate with thebackend server

Benefits:flexible, need not be restricted topredefined queries

Problems:




Security: passwords available at clientsite, all database operation possibleMore code shipped to clientNot appropriate across organizations, orin large ones like universities

Three Tier ModelCGI Program

DatabaseServer

Application/HTTP

ServerServlets

JDBC

Network

HTTP/Application Specific Protocol




Client Client Client

Three-tier Model (Cont.)

E.g. Web client + Java Servlet usingJDBC to talk with database serverClient sends request over http or

application-specific protocolApplication or Web server receivesrequestRequest handled by CGI program or




servletsSecurity handled by application atserver

Better securityFine granularity security

End of Chapter



The Result of loan inner

join borrower on loan.loan- number = borrower.loan-

number




e esu o oan e

outer join borrower on loan-number




The Result of loan naturalinner join borrower




Join Types and JoinConditions




The Result of loan natural

right outer join borrower




e esu o oan u

outer join borrowerusing(loan-number)




the Bank Database




―record based logical model‖ Ky model mundeson shikim dhepershkrimin e te dhenave ne nivelin

logjike dhe shikues.Quhet keshtu sete dhenat na ipen ne forme tefiksuare .Dallojme disa modele tekesaj trajte si

1. Modeli racional(rational model)2. Modeli I rrjetes(network model)3. Modeli hirearkik(hierarchical model)4 Ndryshimet ne mes te




4. Ndryshimet ne mes temodeleve(differences among themodels)

Nje shembull tjeter I

modelit relacionalcustomer-nameCustomer-id

customer-street

customer-city

account-number

Johnson

Smith

Johnson

Jones

Smith

192-83-7465

019-28-3746

192-83-7465

321-12-3123

019-28-3746

Alma

North

Alma

Main

North

Palo Alto

Rye

Palo Alto

Harrison

Rye

A-101

A-215

A-201

A-217

A-201

Atributet




S em u i nje aze re aciona e



―modeli hierarchical‖

Ky model eshte i ngjashem sikurse ai irrjetes me dallim te vetem ku organizimi ite dhenave behet ne forme te rrenjes

d.m.th fillohet nga nje trung dhevazhdohet me tej me te ,si ne figuren eparaqitur me poshte

RRENJAJonhson

Smith

Hayes




Hayes

A-101 A-201

―Differenca ne mes te

modeleve‖ Modeli relacional dallon nga ai irrjetes dhe hirearkik ne ate pasinuk perdore ―linke ‖ dhe―pointera‖,perderisa modelirelational i lidhe te dhenat ne bazete vlerave te tyre qe i permbajne.




Transformimi i modeleve

relacionale ne SQLNe vazhdim do te shohim se si

nje model e ne veqanti modeli E-Rshprehet ne gjuhen e SQL-se.Parase gjithash le te marrim nje model

logjike te bazes se te dhenave teparaqitur si me pare (te modelifizike dhe logjike ).




Paraqitja e nje modeli logjike



Paraqitja e ER-se ne SQL(1)

Pershkrimi I atributeve tjera perentitetin e kurseve do te ishte disikeshtu :

Create table kurset(emrikursit

KohakursitNivelikursit

Klasakursit

);




);

Paraqitja e ER-se ne SQLNe paraqitjen e diagramit te mesemeshte bere lidhmeria e te dhenavenga ato dy entitete te shqyrtura ete cilat do te jen te disa llojta edhedo te ceken me vone.



Modeli relacionalSiq shihet nga larte modeli i tilledallohet per nga paraqitja e formesse tije ,sipas trajtes horizontale dhevertikale te te dhenave .Ku ne secilinrresht paraqitet vetem nje atribut Ientitetit te pare ,ndersa ne secilenshtylle vetem nje atribute Ientitetit te dyte .




―relation model‖

Praktikisht modeli I dhene mund teparaqitet ne forme te tabelave te tedhenave dhe lidhjet e tyre jane te

organizuara ne ate menyre qe te dhenat jane te paraqitura ne kuader te njetabele permes te kolonave dhe

rreshtave ,nje paraqitje e tille do tedukej keshtu ATRIBUTET

Emri Mbiemri gjinia id mosha




gj

emri1 mbiemri1 gjinia1 id1 mosha1



―data definition language(DDL)‖

Me keta urdhera mundesohet definimi ite dhenave themelore ne forme tetabelave ,keto te dhena vendosen ne

fajlle te quajtura ―data dictionary‖,kuketo te fundit permbajne ―metadata‖(tedhena mbi te dhenat ne ate baze),nje

shembull i tille do te ishte ky ne vazhdim:Create table studenti(

Emri char(30),

Mbiemri char(20),




( ),Mosha integer)

―Data manipulation

language(DML)‖ Me ane te ketyre urdherave na mundesohetqe ne kuader te te dhenave te krijuara mepare te bejme Venjen e vlerave te reja

,Fshirjen e tyre ,Ndryshimin etj.Na mundesohet edhe kerkimi i te dhenave dhe

plotesimi I kushteve te ndryshme qe arrihet

me ane te pyetsoreve.Dallojme dy tipe te―DML‖ urdherave ,ato procedurale dhe joprocedurale.Keto te parat kerkojne te dinese cfare te dhena duhen dhe si te merren ato

,ndersa te dytat kerkojn te dine se cfare tedhena te duhen pa e specifikue se si me I




dhena te duhen pa e specifikue se si me Imarre ato.

Disa te dhena te entiteteve

Ne vazhdim per ilustrim temanipulimit dhe punes me urdheratSQL marrim disa entitete dhe

atribute te tyre te dhena permestabelave te meposhtme .




Tabela ―account‖




Tabela ―deposite‖




Tabela ―loan‖




Tabela ―borrower‖




Tabela ―branch‖




Tabela ―payment‖




DML-SQL

Nje shembull se si te merren te dhenat ngabaza eshte ky qe rekordi ―customer-id‖kerkohet te jet ‖192-83-7465‖

select customer.customer-name

from customer where customer.customer-id = ‗192-83-

7465‘

Sqarimet ne lidhje me te dhenat e mesipermete cilat jane marre :

Me ane te urdherit ―select‖ behet zgjedhja e

te dhenave qe deshirojme me I pa me emer tefushes dhe tabeles,me urdherin ―from ‖




tregohet vendi se ku ato duhet te shihen(pratabela),me urdherin ―where ‖ ipet kushti qeato duhet te plotesojne.

DML-SQLShembull tjeter i veprimeve me urdheratSQL eshte dhene si me poshte :Te gjindet ―account balances‖nga te gjithe― customer‖ me ―customer-id=192-83-7465‖ select account.balance

from depositor , account where depositor.customer-id = ‗192-83-7465‘and

depositor.account-number =account.account-numberUrdherat e ketij pyetsori jane te njejte meate te meparshmin ,dallimi qendron ne

faktin se ketu jane perdorur dy kushte tekerkimit te te dhenave dhe ate permes teoperatorit ―and‖(dhe ) I cili do te




operatorit and (dhe ) I cili do te permendet me vone .

Shfrytezuesit e bazave te

te dhenaveShfrytezuesit jane me menyra tendryshme te shikimit te te dhenave p.sh

Aplikuesit e programit – I shohin tedhenat permes urdherave DML

Shfrytezuesit e avancuare – punojne mepyetsore e keshtu me radhe ,varesishtnga niveli I njohurive kemi edhe menyra

te ndryshme te qasjes se te dhenave nenje baze te te dhenave




Elementet themelore ne SQLStruktura bazikeOperatoret e bashkesive

Funksionet AggregateVlerat zerroNenpyetsoret (nested subquerys)Relacionet e perfituaraShikimet (Views)Modifikimi I bazesRelacionet e lidhjes (Joined Relations)Data Definition LanguageEmbedded SQL ODBC and JDBC




Embedded SQL, ODBC and JDBC

Struktura bazeLe te marrim nje shembull te te

dhenave per nje baze relacionale meane te tabelave te meposhtme dheshqyrtojme lidhjen e te dhenave me

relacionet algjebrike (matematike).




Skema e marre ne shembull




Structura bazeSQL eshte e bazuare ne bashkesi dhe relac-ione operacionale me modifikime dhetrashegimeSkema e pergjithshme do te kishte nje

pamje te ketille sipas shembullit tedhene.Nje shembull I tille do te kishte keteforme:

select A 1, A 2, ..., A n from r

1, r

2, ..., r

m

where P A i paraqesin atributet r i paraqesin relacionet

P eshte predikateKy pyetsore eshte ekuivalent me kete shprehjerelacionale algjebrike.




A 1, A2, ..., An (P (r 1 x r 2 x ... x r m ))

Rezultati i nje pyetsori eshte nje relacione.

Urdheri ―select‖ Urdheri select paraqet atributet e nje (apo

disa ) entiteti ne kuader te nje pyetsoriP.sh te gjinden emrat e te gjitha fillialave(branches) ne tabelen huaja (loan)

select branch-name from loan

Kjo do te kishte nje paraqitje ne algjebrenrelacionale si vijon:

branch-name(loan)shenim: SQL nuk e dallon simbolin ‗-‘ nemes te karaktereve

p,.sh ne vend te branch_name merret branch- name Ne vijim do te marrim ‗-‘ .




jShenim : ne SQL shenimi I komandave nuk

ka rrole nga forma e shenimit te shkronjavete vogla apo te medha por I te dhenave po.

Urdheri ―select‖ (vazh.) SQL lejon vlerat e shumefishta ne kuader te

nje pyetsori.Per te bere eliminimin e tille urdheri―select‖perdoret ne kombinim me urdherindistinct dhe ate pas urdherit select.

Te gjinden emrat ne te gjitha filliallat e huase(loan) dhe eliminoj te shumefishtat

select distinct branch-name

from loanNdersa per shikim te te dhenave teteresishme pa perjashtim edhe atyre teshumefishta perdoret urdheri ―select‖ ne

kombinim me all .select all branch-namefrom loan




from loan

Urdheri ― select‖ (vazhd.)

Zgjedhja e pernjehershme e te gjithaatributeve ne nje tabele behet meperdorim te urdherit select si ne vijim

select *from loanUrdheri select mund te permban nevete operator aritmetike, +, –, , dhe /.

P.sh nese merret pyetsori :select loan-number,branch-name,amount 100from loan

Ateher ky do te na jep rezultatin I cilieshte I njejte me ate te huase (loan )




eshte njejte me ate te huase (loan ) por te shumezuare me 100

Urdheri ― where ― Urdheri where na specifikon kushtet te

cilat duhet ti plotesojne atributet eentiteteve te cilat shqyrtohen ne ate raste

Funksion ne lidhmeri me urdherin select.

P.sh me gjete te gjithe numrat e huase ngahuaja (loan) dhe filiala Perryridge me numerte huase me te madhe se sa $1200.select loan-number

from loanwhere branch- name = ‗ Perryridge‘ and amount > 1200Te dhenat ne kuader te nje pyetsori mund te

kerkohen edhe me ane te operatoreve logjikeand, or dhe not. Ne te dhena mund te aplikohen edhe




Ne te dhena mund te aplikohen edheoperatoret aritmetike.

Pershkrimi i rrolit te

pyetsorevePyetsoret formohen me ane te ketyrekritereve te pershkruara me poshte:

Emrin e tabeles (table)Radhitjen e informates (sortim)

Kushtezimin e marrjes ne konsiderim

te informatesKriterin e zgjedhjes sipas operatoritlogjike ,aritmetike,te bashkesive.

Edhe ndonje elemente tjeter shtese




Rolet e operatoreve ne

organizimin e pyetsoreveNe funksion te pyetsoreve dallojme disatipe te operatoreve te cilet perdorenper ndertim te pyetsoreve :1.Operatoret logjike :―and‖(operatori dhe),―or‖(ose),‖eqv‖(ekuivalent),‖imp‖(implikacion),‖xor‖(ekslusiv ose),‖not‖(jo).

2.Operatoret artimetike:+(mbl.),-(zbr.),*(shum.),/(pjes.),\(pjes.iplote),^(fuqi),mod(modulo).3.Operatoret krahasues(racional):=(bara.)<(vog.),>(madh.),<>(!=)(ndrysh.),<=(!<)(vog.osebara.),>=(!>)(madhe ose baraz.).




.), ( )(m z.).

Operatoret

4.Operatoret tekstual(string):

&(operatori i bashkimit),‖like‖(operatori

sikurse),‖not like‖(operatori i ciliperjashton vlerat sikurse ato tezgjedhurat).

5.Operatoret e perzier jane: ―between‖(ndermjet),‖in‖(ne),‖is‖(nga).

Ne vijim shohim format e paraqitjes se

operatoreve te tille veq e veq.




er or m opera orevelogjikePerdorimi i operatorit logjike ―and‖ nepyetsore (ne trajten konstruktive )

realizohet sipas funksionit te tij qeparaqitet me tabelen vijuese

p q pq

E vertet E vertet E vertet

E vertet E pavertet E pavertet

E pavertet E vertet E pavertetE pavertet E pavertet E pavertet




er or m operatorevelogjike(v-1)

Rroli i operatorit logjike ―or ‖realizohet sipas vetive te tij teparaqitur ne trajten e meposhtme

p q pq

T T T

T

T

T T




T T



Forma paraqitese eoperatoreve logjikeOperatoret logjike ,perveq operatorit―not‖, jane operator binar(dyshe) ,ndersa―not‖ eshte unar(njesh). forma paraqitesee tyre eshte e njejte ,ndersa e operatorit―not‖ dallon.Kete do ta japim me posht.

Operatori ―and‖-paraqitet si me poshte

[shprehja1] and [shprehja2]

Ngjashem paraqitet ―or‖.

Operatori ―not‖ ka kete forme teparaqitjes :p.sh

Not [shprehja e dhene ]<188




Not [shprehja e dhene ] 188

Forma paraqitese eoperatoreve aritmetike

Operatori ―+‖ ka kete trajte

[shprehja1] + [shprehja2]

Ne menyre analoge behet edheparaqitja e operatoreve te tjere p.sh

[shprehja1] - ([shprehja2] *[shprehja3])

Me cka se pari eshte kryer shumzimi i

shprehjes2 me ate 3 dhe me pas janezbritur nga shprehja1



Vecorite e operatoreve (v-1)

Operatori <> ka funksionin ekerkimit te informates tendryshme nga ajo ne shqyrtim ,

―between‖ na mundeson kerkimine informatave ndermjet vleravete cekura ,‖like‖ na mundeson

kerkimin e informatave tengjashme me ate te shqyrtuar .




Forma paraqitese eoperatoreve krahasues

Operatori ―=‖ ka kete paraqitje temeposhtme:

[shprehja] =―dicka‖. Ngjashem paraqiten edhe operatoret e

tjere te krahasimit e nje shembull itille eshte edhe ky:

[shprehja1] !< ―e dhena‖.




orma paraqitese eoperatoreve tekstual

Nje trajte e paraqitjes se operatorit ―&‖ dote ishte[emri] & [mbiemri] , si rezultat do te kishim :Emrimbiemri.Ndersa forme tjeter e ndarjes se te dhenaveeshte kur operatori perdoret ne kete menyre:[numri i shtepise] & ―‖ &[emri i rruges]

Nese numri do te ishte 6 dhe emri i rrugesA.Jashari ,ateher do te kishim rezultatin6 A.Jashari,d.m.th me zbraztesi ne mes te

tyre.Operatori ―like‖-perdoret ne formen emeposhtme




[shprehja] Like ―A[bc]‖

Operatori tjeter perdoret njejte.

Forma paraqitese eoperatoreve te perzier

Paraqitja e operatorit ―between‖ eshtesi me poshte

[shprehja] between A and BOperatori ―in‖ ka paraqitje temeposhtme

[shprehja] in (vlera1,vlera2)[shprehja] is Null




Perdorimi i ―wildcards‖-ve




Urdheri where (vazh.)

Ne vazhdim shohim nje shembull teperdorimit te operatorit te krahasimitbetween me urdherin ―where‖ P.sh te gjindet numri I huase nga

huaja me vlere ne mes te $90,000 dhe$100,000 (kjo eshte , $90,000 dhe$100,000)

Nje gje e tille ipet permes pyetsorit temeposhtem

select loan-number from loan where amount between 90000 and 100000



Riemrimi i operacionit

Permes urdherave te SQL lejohetriemrimi I relacioneve dhe atributevepermes urdherit as :

emri I vjeter as emri I ri Te gjindet emri ,numri I huase dhesasia e huase e te gjithe klienteve; te

riemrohet emri I kolones loan- number(numri I huase ) si loan-id.

select customer-name, borrower.loan-number as

loan-id, amountfrom borrower, loan where borrower.loan-number = loan.loan-number




Qiftet e variablave (nga ketupermireso)

Keto tipe te variablave jane tedefinuara ne urdherin from permeste urdherit as .Gjeni emrat e klienetve dhe numrat etyre te huase per te gjithe kliente qekane hua ne ndonje filialle.

select distinct T.branch-namefrom branch as T, branch as S

h T S d S b h it „B kl ‟

gjeni emrat e te gjitha filiallave te cilat kanegjendje(assets) me te mire se sa nje filialle ne

Brooklyn.

select customer-name, T.loan-number, S.amountfrom borrower as T, loan as Swhere T.loan-number = S.loan-number




where T.assets > S.assets and S.branch-city = „ Brooklyn‟



Radhitja e te dhenaveTe radhiten ne menyre alfabetike emrat eklienteve (me emra te ndryshem) qe kanehua ne filiallen Perryridgeselect distinct customer-name

from borrower, loanwhere borrower.loan-number = loan.loan- number

andbranch-name = ‘Perryridge’ order by customer-name Ne mund te specifikojme desc (z-a) per

radhe nga e madhja kah e vogla dhe measc (a-z) per radhitje te kundert, persecilin atribute; radha asc eshte en nk pt




nenkuptuare.P.sh te radhiten emrat e klienteve me radhen desc

Vlerat e shumefishtaNe raste te perseritjes se te dhenave ,

SQL mund te definon se sa kopje jane nrezultate.Format shumevepruese te operatorevealgjebrike – jane dhene relacionet qeveprojne ne shumebashkesi r 1 dhe r 2:1. (r 1 ): nese jane c 1 kopje te qiftit t 1 ne

r 1, dhe t 1 e ploteson zgjedhjen ,, ateher

jane c 1 kopje nga t 1 ne (r 1). 2. A (r) : per qdo kopje te qiftit t 1 ne r 1, ekziston

kopja e qiftit A (t 1) ne A (r 1) ateher A (t 1) shenon projeksionin e qiftit te vetem t 1 .

3. r 1 x r 2 : nese jane c 1 kopje te qiftit t 1 ne r 1 dhe c 2 kopje te qiftit t 2 ne r 2, ateher jane c 1 x c 2 kopje te qiftit t 1. t 2 ne r 1 x r 2




2 pj q f 1 . 2 1 2

Vlerat e shumefishta (vazh.)

P.sh : Supozojme nje relacion ne mes tedy bashkesive r 1 (A, B ) dhe r 2 (C ) si meposhte :r 1 = {(1, a ) (2,a )} r 2 = {(2), (3), (3)}

Ateher B (r 1) do te jet {(a), (a)}, kuB (r 1) x r 2 do te jet{(a ,2), (a ,2), (a ,3), (a ,3), (a ,3), (a ,3)}

SQL semantika per vlera teshumefishta eshte :select A 1,, A 2, ..., A n from r

1, r

2, ..., r

m

where Pekuivalente me kete shprehjerelacionale algjebrike :




relac onale algjebr ke

A 1,, A 2, ..., An ( P (r 1 x r 2 x ... x rm ))

Operatoret e bashkesiveOperacionet e bashkesive union, intersectdhe except operojne ne relacione dhe I

pergjigjen operacioneve algjebrike si Secili nga operatoret e mesipermautomatikisht eliminon vlerat eshumefishta; per shikim te te gjitha tedhenave edhe qe perseriten perdorenoperatoret union all, intersect all dheexcept all.Supposojme se nje qifte perseritet m herene r dhe n here ne s, ateher , do te kishim :

m + n here ne r union all smin(m,n) here ne r intersect all s

max(0, m – n) here ne r except all s




max(0, m n) here ne r except all s

Operatoret e bashkesive

(vazh.)Gjeni te gjithe klientet te cilet kanehua ,nje llogari apo edhe qe te dyja :

(select customer-name from depositor )except(select t from

(select customer-name from depositor )intersect(select customer-name from borrower)

gjeni te gjithe klientet qe kane llogari por jo edhe hua

(select customer-name from depositor )union(select customer-name from borrower)

gjeni te gjithe klientet te cilet kane edhe hua dhe llogari




(select customer-name from

borrower)

Funksionet AgregateKeto funksione veprojne ne kuader te

nje bashkesie te vlerave ne kuader tenje kolone dhe japim nje vlere tecaktuare

avg: vleren mesataremin: vleren minimalemax: vleren maximale

sum: shumen e vleravecount: numrin e vlerave




Funksionet Agregate(vazh.)Te gjindet mesatarja e ballances sellogarive ne filiallen Perryridge .

gjeni numrin e depozitoreve me emra te ndryshem ne banke

gjeni numrin e qifteve ne relacionin e klienteve

select avg (balance) from account

where branch-name = „Perryridge‟

select count (*)

from customer

select count (distinct customer-name)

from depositor




Funksionet Agregate– Group By

Gjeni numrin e depozitoreve persecilen filialle.

shenim: Attributet ne urdherin select jashte

funksioneve agregate

duhet te hyne ne urdherin group by

Select branch-name, count (distinct customer-name)from depositor, accountwhere depositor.account-number = account.account-

number

group by branch-name




Funksionet Agregate – Having

ClauseGjeni emrat e te gjitha filiallave nete cilat e mesmja e llogarise se

ballancuare eshte me shume se$1,200.

shenim: predikatet ne urdherin having jane aplikuar pase formimitte grupit perderisa predikatet ne urdherin where jane aplikuare paraformimit te grupit

select branch-name, avg (balance)from account

group by branch-namehaving avg (balance) > 1200




Vlerat zerroKa mundesi qe nje atribute ne nje qifterelacionale te mos kete vlere ,kjo njihet si

vlere zerronull –shpreh nje vlere te panjohur apo edhevleren e cila nuk ekziston.

P.sh gjeni te gjithe numrat e huase te cilet

jane ne relacionin e huase me vlere zerro perllogari. select loan-numberfrom loanwhere amount is null

Secili rezultat I ndonje veprimi aritmetikeme zerron na kthen vleren zerroP.sh 5 + null kthene null

Funksionet agregate e injorojne vlerenzerro




erat zerro s pre jet ogj eme te

Cdo krahasim me zerro eshte vlere epanjohurP.sh 5 < null ose null <> null ose null = nullTri vlerat logjike me zerro :

OR: (e panjohur or e vertet ) = e vertete , (epanjohur or e pavertete ) = e panjohur

(e panjohur or e panjohur ) = e panjohurAND: (e vertete and e panjohur ) =e panjohur ,

(e pavertete and e panjohur ) = e pavertete ,( e panjohur and e panjohur ) = e panjohurNOT : ( not e panjohur ) = e njohur―P eshte e panjohur ” eshte e vertete nese

prediakati P eshte I panjohurRezultati I urdherit where ne predikateeshte I pavertete nese njihet si I panjohur




Vlerat zerro dhe funksionet

agregateNjehso gjithe sasine e huase

select sum (amount)

from loan Urdherat e mesiperm I injorojne llogaritezerroRezultati eshte zerro nese nuk ka llogari te

ndryshem nga zerro,kjo d.m.thTe gjitha funksionet agregate perveqcount(*) I injorojne qiftete me vlere

zerro ne atributet ne funksioninagregate.




Nested SubqueriesNje nenpyetsore eshte I marreme urdherat select-from-where

si shprehje e permbajtur ne njepyetsore tjeter.Nje pune me e shpeshte e

nenpyetsorit eshte teperformoje testimin e bashkesisese antareve ,bashkesise sekrahasimeve dhe numrit kardinal

te tyre.




Shembulli I pyetsoritGjeni te gjithe klientet qe kanellogari dhe hua ne banke.

gjeni te gjithe klientet qe kane hua ne banke por nuk kane llogarine te

select distinct customer-name

from borrowerwhere customer-name not in (select customer-name

from depositor)

select distinct customer-namefrom borrowerwhere customer-name in (select customer-name

from

depositor)




Shembull pyetsoriGjeni te gjithe klientet te cilet kanellogari dhe hua ne filiallen Perryridge

Note:ky pyetsore mund te rishkruhet edhe ne nje forme me te thjeshte.

select distinct customer-namefrom borrower, loanwhere borrower.loan-number = loan.loan-number and

branch-name = “Perryridge” and

(branch-name, customer-name) in

(select branch-name, customer-namefrom depositor, accountwhere depositor.account-number =

account.account-number)




Krahasimet e bashkesive

Gjeni te gjitha filiallat te cilat kanete ardhura(gjendje (assest)) me temire se sa nje filialle ne Brooklyn.

I njejti pyetsore kur merret urdheri some

select branch-namefrom branchwhere assets > some

(select assetsfrom branchwhere branch-city = ‘Brooklyn’)

select distinct T.branch-name

from branch as T, branch as Swhere T.assets > S.assets and

S.branch-city = ‘Brooklyn’




Perkufizimi I shprehjeveFormula F <e ploteson nje kusht te dhene

> per ndonje (some )r t r e tille qe( F < e ploteson nje kushte te dhene > perate t ) ku shprehja <e ploteson nje kushte tedhene > eshte njera nga :

0

5

6

(5< per

ndonje) =vertete 0

5

0

) = e pavertete

5

0

5

(5 perndonje

) =e vertete (pasi 0

5)

(5< perndonje

) =e vertete(5 =perndonje

(= per ndonje ) neDhe , ( per ndonje ) nuk eshte ne te




Definimi i urdheraveFormula F <e ploteson kushtin >all r t r (F <e plotesonkushtin> t)

0

5

6

(5< per te gjitha ) =e pavertete

6

10

4

) =e vertete

5

4

6(5 per te gjitja ) = e vertete (pa rastet 5 4 dh e 5 6)

(5< per te gjitha

(5 = per te gjitha

( te gjitha ) nuk eshte ne

) =e pavertete



nbraha-bazat e te dhenave 362(= te gjitha ) ne

shembull i dhene

Gjeni emrat e te gjitha filiallave tecila kane gjendje (asset) me te mirese sa tere ato ne Brooklyn.

select branch-name

from branchwhere assets > all

(select assetsfrom branch

where branch-city = „Brooklyn‟)




Verifikimi I relacioneve te

zbrazeta

Kushti exists na kthene vleren esakte nese argumenti Inenepyetsorit eshte jo I

zbrazet.exists r r Ø

not exists r r = Ø




ShembullGjeni te gjithe klientet te cilet

kane llogari ne te gjitha filiallatqe gjenden ne Brooklyn.select distinct S.customer-namefrom depositor as S

where not exists ((select branch-namefrom branchwhere branch-city = „Brooklyn‟)

except(select R.branch-namefrom depositor as T, account as Rwhere T.account-number = R.account-number and

S.customer-name = T.customer-name))

shenojme se X – Y = Ø X Y




Testimi i vlerave te shumefishtaKjo arrrihet permeste kushtit unique I

cili kthene vleren e sakte kur nuk kemivlera te shumefishta ,p.sh te gjendente gjithe klientet te cilet kane vetemnje llogari ne filiallen perryridge.

select T.customer-namefrom depositor as Twhere unique (

select R.customer-namefrom account, depositor as Rwhere T.customer-name =

R.customer-name and R.account- number = account.account-number andaccount.branch- name = ‗ Perryridge‘)




Shembull I nenpyetsoritNe kuader te nje nenpyetsori

kerkimi I vlerave te shumfishtabehet me ane te kushtit not uniquep.sh gjeni te gjithe klienete te ciletkane se paku dy llogari ne filiallenPerryridge.

select distinct T.customer-namefrom depositor T

where not unique (select R.customer-namefrom account, depositor as Rwhere T.customer-name = R.customer-name

and

R.account-number = account.account-numberand

account.branch-name = ‘Perryridge’)




Views(shikimet )Shikimet na sherbejne per shikim

te te dhenave por jo edhe permodifikim te tyre sikurse nenivelin logjike te tyre ,per krijimte tyre perdoret urdheri :

Veqori themelore e tyre eshte se

behet ruajtja e pyetsoreve tecaktuare ne kuader te asaj bazete te dhenave

create view emri I shikimit as <shprehja e pyetsorit >




Shembull

Te krijohet nje shikim I cili ka nevete filiallat dhe kliente

gjeni te gjithe klientet nga filialla Perryridge

create view all-customer as

(select branch-name, customer-namefrom depositor, accountwhere depositor.account-number = account.account-

number)union

(select branch-name, customer-namefrom borrower, loanwhere borrower.loan-number = loan.loan-number)

select customer-namefrom all-customerwhere branch-name = „Perryridge‟




Relacionet e perftuaraSQL lejon perdorim te shprehjeve ne

nenpyetsore dhe kjo behet te urdheri wheremirepo rezultati i fituare duhet teriemrohet p.sh te gjindet mesatarja ellogarive ne balance te atyre filiallave me

mesatare te tille me te madhe se sa $1200.select branch-name, avg-balancefrom (select branch-name, avg

(balance) from accountgroup by branch-name)as result (branch-name, avg-

balance)where avg-balance > 1200




Urdheri me (with)Urdheri me(with ) ju lejonshikimeve(views) te definohen lokalishtne nje pyetsore e jo ne forme globale.

Gjeni te gjitha llogarite me balancemaksimale

with max-balance (value ) as

select max (balance )from account select account-numberfrom account, max-balance

where account.balance = max- balance.value




Shembull i nje pyetsori me te

nderlikuareGjeni te gjitha filiallat ku llogariatotale e depositit eshte me e madhese sa mesatarja e llgarise deponuese

ne te gjitha filiallat with branch-total (branch-name, value) as

select branch-name, sum (balance)from account group by branch-name with branch-total -avg(value) as select avg (value)from branch-total

select branch-name from branch-total , branch-total-avgwhere branch-total.value >= branch-total-avg.value




o i i imi i azes se tedhenave

Me urdherin Delete mundesohet fshirja e tedhenave te nje rekordi por jo edhe te tabelesp.sh te fshihen te dhenat e huase ngaperryridge :delete from accountwhere branch-name = ‘Perryridge’

Te fshihen te gjithe klientet ne secilen filiallene Needham city.delete from accountwhere branch-name in (select branch-namefrom branchhere branch-city = ‘Needham’)delete from depositor

where account-number in(select account-numberfrom branch, accountwhere branch-city = ‘Needham’ and branch.branch-name =

h )



nbraha-bazat e te dhenave 373account.branch-name)

ShembullTe fshihen te gjitha rekordet ne tegjitha llogarite me ballanca me te

vogel se sa mesatarja

delete from accountwhere balance < (select avg (balance)

from account)




Modifikimi I bazes – Insertimi(vendosja e te dhenave )

Te shtohet nje cifte ne accountinsert into accountvalues (‗A-9732‘, ‗Perryridge‘,1200)

ose ne forme ekuivalenteinsert into account (branch-name,balance, account-number)values (‗Perryridge‘, 1200, ‗A-9732‘)

Te shtohet nje cifte I te dhenave ne

account me balance zerroinsert into accountvalues (‗A-777‘,‗Perryridge‘, null )




o m azes se edhenave Insertimi

Nese I japim te gjithe klienteve sidhurate nga 200 $ ne filiallenPerryridge . Nese numri I huase merretsikurse numer I llogarise per llogarinereinsert into account

select loan-number, branch-name, 200from loanwhere branch-name = ‗Perryridge‘

insert into depositorselect customer-name, loan-

numberfrom loan, borrowerwhere branch-name = ‗ Perryridge‘

and loan.account-number= borrower.account-number




Modifikimi I bazes - UpdateMe kete urdher mundesohet

ndryshimi I vlerave ne nje kolone tetere .p.sh te rriten vlerat e tegjitha llogarive me balance me te

madhe se sa $10,000 me 6%, tegjitha llogarite tjera me 5%.update accountset balance = balance 1.06

where balance > 10000update accountset balance = balance 1.05

where balance 10000

Kjo u mundesua me dy update ne radhensi me larte mund te behet edhe meurdherin case si me poshte



Urdheri Update ne shikimeTe krijohet nje view per te gjitha huate ne

relacionin e huase , duke mshefur atributine llogarise create view branch-loanas

select branch-name, loan- numberfrom loan

Shtoje nje rekord ne branch-loaninsert into branch-loan values (‗Perryridge‘, ‗L-307‘)

ky shtim duhet te paraqitet me shtim teciftit(‗L-307‘, ‗Perryridge‘, null )ne relacionin e huase

Urdheri Updates ne shume shikime komplekseeshte I veshtire dhe I pamundur tepershtatet dhe per kete nuk lejohet.




TransactionsTransakcioni eshte nje varge I pyetsoreve dheurdherave update te ekzekutuara si nje teresi

Transakcionet fillojne ne menyre te shprehurdhe t epercaktuara me njeren nga paraqitjetcommit work: ku kryen te gjitha update ne atetransakcione te asaj baze

rollback work: I cbene te gjitha update tekryera me ate transakcion

Shembull:Bartja e parave nga nje llogari netjetren behet ne dy hapa:merr nga nje llogari

dhe I ven ne tjetrenNese njeri hape kryhet por tjetri jo ateherbaza eshte ne nje gjendje jo te pershtatshmePer kete duhet te plortesohen qe te dy ketokushte ose asnjeriNese nje hape ne nje transakcion deshtonateher ata kthehen me rollback work.Rollback I nje transakcioni jo te suksesshemb h t t m tikisht n stin p ishj s s



nbraha-bazat e te dhenave 380behet automatikisht, ne rastin e prishjes se

b h b dh 381

Transakcioni (vazh.)

Ne shume sisteme te baza te te dhenave,nje urdheri I SQL ekzekutohetsuksesshem ne menyre automatike

Secili transakcion do te perbehetnga njeurdher i vetem

Veprimi automatike zakonisht lihet anashduke lejuare veprimin e transakcioneve tetjera ne ate baze dhe kjo mvaret se cilido te veproje ne ate sistem

Opcion tjeter ne SQL 1999: e permbyll

urdherin me begin atomic…

end




b h b t t dh 382

Relacionet e lidhjesRelacionet e lidhjes marrim dy relacione

dhe si rezulta na kthejne nje relaciontjeter.Keto operacione merren si nenpyetsore nekuader te urdherit from

Kushtet e lidhjes – duhet te percaktohencilat cifte hyne ne lidhje dhe cfarerezultati dote fitohet.

Tipet e lidhjes – duhet percaktuare ciftette cilat I pergjigjen apo jo cifteve tjerane ate lidhje varesisht nga zgjedhja e tipitte lidhjes.

Tipet e lidhjes

Lidhja e brendshmeLidhja e majte e jashtmeLidhja e djathte e jashtme

Lidhja totale

Kushtet e lidhjes

Natyralene <predicate>Duke marre ( A1, A2, ..., An)



nbraha-bazat e te dhenave 382Lidhja totale

nb h b t t dh n 383

Relacionet e lidhjes – shembull

Relacioni loan

Relacioni borrower


Jones

Smith

Hayes

L-170

L-230

L-155

amount

3000

4000

1700

branch-name

Downtown

Redwood

Perryridge

loan-number

L-170

L-230

L-260




nbraha bazat e te dhenave 384

shembull i lidhjes se brendshmdhe te jashtme te majte

loan inner join borrower onloan.loan-number =borrower.loan-number

loan left outer join borrower on loan.loan-number = borrower.loan-number

branch-name amount

Downtown

Redwood

3000

4000


Jones

Smith

L-170

L-230

loan-number

L-170

L-230

branch-name amount

Downtown

Redwood

Perryridge

3000

4000

1700


Jones

Smith

null

L-170

L-230

null

loan-number

L-170

L-230

L-260





Pershkrimi i lidhjes inner

Nga shembulli i mesipermloan inner join borrower onloan.loan-number = borrower.loan-number

shihet se jane marre te gjitha fushat eanes se majte dhe ato te djathte perte cilat ekzistojne fushat koresponduesete atributeve dhe nuk jane zerrofusha, ne te dy tabelat e dhena ,meinicim nga tabela e majte dhe fushatlidhese te marra ne ate lidhje paraqiten

dy here ne dalje





Pershkrimi i lidhjes outer left

Ne shembullin e marre me larte loan left outer join borrower on

loan.loan-number = borrower.loan-

numberShihet se kjo lidhje realizohet meane te marrjes se te dhenave nga

ana e majte dhe elementetkoresponduese te asaj te djathteedhe ne rastin kur nuk kemi vlera teatributit ne te djathte(d.m.th kurkemi vlera zerro) dhe gjateparaqitjes behet edhe paraqitja evlerave(fushave ) te lidhjes dhe ate

dy here



nbraha bazat e te dhenave 386dy here


Pershkrimi i lidhjes outer te

djathte

Kjo eshte e ngjashme me ate terealizimit te majte vetem tanene shikim merret tabela e pare sitabele e djathte dhe vleratlidhese te atyre tabelave merrenedhe per atributet te cilat kanevlerat zerro.





Shembull I lidhjesloan natural inner join borrower

loan natural right outer join borrower

branch-name amount

Downtown

Redwood

3000

4000

customer-name

Jones

Smith

loan-number

L-170

L-230

branch-name amount

Downtown

Redwood

null

3000

4000

null

customer-name

Jones

Smith

Hayes

loan-number

L-170

L-230

L-155





Pershkrimi i lidhjes natural

Lidhja natural eshte nje lidhje etipit te njejte sikurse innerperveq te dallimit se gjate asajlidhje fushat lidhese ne mes tedy tabelave nuk na paraqiten dyhere ne dalje te te dhenave qeshihet edhe nga shembulli I marreme larte




Pershkrimi i lidhjes naturale

,outerEdhe ketu vlene te ceket se lidhjabehet njesoj si te cilado lidhej e

jashtme per dallim se ketu fushatlidhese te tabelave te cilat naparaqiteshin dy here me heret tani

na paraqiten vetem nje here dhe etere paraqitja tjeter eshte e njejte,e ate te marre te lidhjes se

jashtme




Shembull I lidhjesloan full outer join borrower

using (loan-number)

Gjeni te gjithe klientet kane nje llogari apo hua (por jo qe te dyja ) ne banke.

branch-name amount

Downtown

Redwood

Perryridge

null

3000

4000

1700

null

customer-name

Jones

Smith

null

Hayes

loan-number

L-170

L-230

L-260

L-155

select customer-name

from (depositor natural full outer join borrower ) where account-number is null or loan-number is null




Pershkrimi i lidhjes full

Kjo realizohet me marrje te tegjitha fushave nga te dy tabelatduke perfshire fushat me atributezerro dhe ato pa atribute zerrosi dhe paraqitjen e te dhenave nedalje vetem nje paraqitje tefushes lidhese te tyre




Data Definition Language

(DDL)Skema e cdo relacioniDomena e vlerave te shoqeruara per

secilin atribute.Integrity I kushteveBashkesia e indekseve te ruhet per

secilin relacion.Sigurimi dhe autorizimi per secilinrelacion.Struktura fizike e te dhenave persecilin relacion ne disk.




Tipet e te dhenave ne SQLchar(n). Per karakter me gjatesi n. varchar(n). Variable e karaktereve megjatesi n.int. Integer (numer I plote ).smallint. Integer I vogel.

numeric(p,d). Numer me decimale me p shifra nga n te tere ne te djathet te pikes .real, double precision. Floating point dhedouble.

float(n). Floating point number,me gjatesin shifrash .Null lejohet ne tere tipet e te dhenave .Deklarimi I atributi not null ndalon qe ajo

vlere te jet null per ate attribute.create domain kushti I tille ne SQL-92krijon per shfrytezuesin tipin e te dhenave

create domain person-name char(20) not null




Date/Time tipet ne SQL (vazh.)date. Datat me (4 shenja ) te vitit , muajindhe daten p.sh date ‗2001-7-27‘ time.kohen e dites , ne ore, minuta dheseconda.p.sh. time ‘09:00:30‘ time ‘09:00:30.75‘ timestamp: date plus koha e dites

p.sh. timestamp ‗2001-7-27 09:00:30.75‘ Interval: periode te kohes

p.sh. Intervali ‗1‘ dite

Ndarja e vleres se date/time/timestamp na jepnje intervalVlerat e intervalev mund te shtohen ne vlerat edate/time/timestamp

Mund te extraktohen vlerat e fushaveindividuale nga date/time/timestamp

p.sh. extract (year from r.starttime)

Gjithashtu mund edhe te largohen vlerat nga

tipet e te dhenave date/time/timestamp.sh. cast <strin -valued-ex ression> as date



p p


Krijimi I TabelaveNje relacion I realizohet me komandencreate table:create table r (A 1 D 1, A 2 D 2, ..., A n D n ,integrity-constraint1),

...,(integrity-constraintk))

r eshte emri I relacionit

Secila A i eshte nje emer I atributit ngarelacioni r

D i eshte tipi I te dhenave per atributet A i

P.sh :create table branch (branch-name char(15) not null,branch-city char(30),assets integer)




Integriteti i kushteve ne

Create Tablenot nullprimary key (A 1, ..., A n )check (P), ku P eshtepredicate

p.sh : te deklarohet branch-name si primary key perbranch dhe siguro qe vlerat e assets te jene j o-negative.

create table branch(branch-name char(15),branch-city char(30)assets integer,primary key (branch-name),

check (assets >= 0))

primary key ne nje deklarim automatikisht nenkuptohet jo zerro vlere




Urdherat Drop dhe Alter TableUrdheri drop table fshine nje tabele ne

teresi kjo d.m.th edhe gjithe relacionet mete .Urdheri alter table mundeson shtimin eatributeve ne kuader te nje relacioni

ekzistues .alter table r add A D

ku A eshte emri I attribute qe shtohet ne

relacionin r dhe D eshte domena e A. krejt ciftet ne relacion merren si null pervlerat e atributeve te reja .

alter table mund te meret edhe per fshirjete attributeve ne nje relacionalter table r drop A

ku A eshte emri i attributit ne relacionin r




Baza te tjera relacionale

QBE(query by example-access)Nje baze relacionale e cila do teshqyrtohet eshte edhe MSAccess.

Ne vazhdimesi do te dallojmeelementet themelore ne lidhje mepershkrimin e te dhenave permestrajtes QBE .Kjo realizohet nepanelin ―disajn‖ te pyetsoreve tepershkruare si me poshte .Kjo narealizohet permes disa tipeve te

pyetsoreve .



Pyetsoret e trajtes ―crosstab

query wizard‖ Ndertimi i ketyre pyetsoreve

realizohet me zgjedhjen e opcionit―crosstab query wizard‖ ,edhe ketasherbejne per veqim te te dhenave ,ene radhe te pare per krahasim te te

dhenave ,por vetem per ato te njetabele.Per ndertim te tyre duhet tezgjedhim te dhenat te cilatdeshirojme ti kemi ne forme shtylle ,ato qe deshirojme ti kemi ne formerreshti dhe ato te shumueshme



Pyetsoret e tipit ―Find

duplicates query wizard‖

Keta formohen me ane tezgjedhjes se opcionit ―findduplicates query wizard‖ dhe nasherbejne per gjetjen e tedhenave te njejta (te shumfishta)te nje tabele apo edhe te njepyetsori .



Njehsimet me ane tepyetsoreve

Dallojme njehsimet sipas te dhenavehorizontale dhe te dhenave vertikale .Realizimi i njehsimit te te dhenave netrajten horizontale(nese te dhenat janeper njehsim ) arrihet ne trajten―disajn‖(konstruktive) te pyetsorit dhe ateduke marre operatoret aritmetike (ne atemenyre qe ne mes te fushave te zgjedhuradhe operatorit te kemi se paku nga njezbraztesi) ne mes te dhenave te dyfushave te ndryshme(apo edhe me shume )

, te njehsuara ne nje fushe te trete dhene opcionin ―Field ‖ te formes ―disajn‖ tepyetsorit ku me pas shtypet ―enter‖ me ckaemerohet fusha e re me ―exp1‖e cila me

vone mund te riemrohet.




Paraqitja e hapesires

njehsuese




Njehsimet me ane te

pyetsoreve(v-1)Njehsimi ne forme vertikale te

dhenave (per ato te dhena per tecilat lejohet njehsimi ) te tabeles,realizohet me ane te pyetsoreve tetrajtes ―simple query wizard‖dhepermes tipit ―disajn‖ Ne tipin ―simple query wizard‖ tedhenat e tabeles njehsohen sipas

ketyre mundesive1. Shuma e teresishme e tedhenave(sum)




Njehsimet me ane te

pyetsoreve (v-2)

2.Njehsimi i vleres mesatare tetyre (avg)3. Njehsimi i vleres minimale tedhenave te asaj kolone (min)

4. Njehsimi i vleres me te madhete te dhenave te asaj kolone

(max)




Njehsimet me ane te

pyetsoreve(v-3)

Njehsimet sipas kolonave mundte behen edhe ne paraqitjen―disajn‖ te pyetsorit dhe ajoparaqitje per dallim nganjehsimi ne tipin ―simple querywizard ‖ na lejon nje mundesi mete madhe te njehsimeve neelementet e shtylles dhe atesipas ketyre operacioneve :




Njehsimet me ane te

pyetsoreve(v-4)Group by(ne grupe)

Sum(shumen e te dhenave )Avg(vleren mesatare)Min(vleren minimale)

Max(vleren maksimale)Count(numeron te dhenat pa fushat ezbrazeta)

Stdev(derivimi standard)Var(menyrat e paraqitjes se tedhenes)




Njehsimet me ane te

pyetsoreve (v-5)

First(vlera e te dhenes se pare neradhe)Last(vlera e te dhenes se funditne radhe)

Expression(sherben per ndertimte fushes per njehsim)

Where(jepet kriteri per tedhenat e shqyrtuara)




Dallimet ne mes te

llogaritjeve ne pyetsoreDallimet themelore ne mes menyrave

te llogaritjeve ne pyetsore per ngamenyra e njehsimit te te dhenavesipas shtyllave dhe rreshtave

qendrojn ne faktin se njehsimet e tedhenave sipas shtyllave jane tekufizuara dhe ate vetem ne katerllojet e permendura te njehsimeve(sum,avg,min dhe max) per tipin epyetsorit ―simple query wizard‖




Dallimet ne mes tellogaritjeve ne pyetsore(v-1)

Ndersa ne formen ―disajn ‖ mezgjedhje te opcionit ―total‖ ne menyne

―insert‖ shtohen mundesit e njehsimevete cekura me pareNjehsimet e te dhenave sipasrreshtave behen pa kufizime te tilla

dhe realizohen per gjitha mundesit tecilat na lejojne operatoret aritmetikete theksuare, d.m.th se njehsimetsipas rreshtave jane njehsime me te―mira‖ te te dhenave se sa ato sipasshtyllave

Llogaritjet me me shume




Llogaritjet me me shumefunksione

Keto llogaritje realizohen me ane te―expresion builder‖-it dhe kjo arrihetkur ne fushen e caktuar te formeskonstruktive te pyetsorit zgjedhim metastin e djathet te miut opcionin―built‖.Ne kete rast kemi mundesi temanipulimit me ane te

funksioneve,konstanteve,operatoreve(logjike,aritmetike,krahasues) si dhe teshprehjeve te paraqitura.Aktivizimi i―expresion builder‖-it realizohet per

tipet e te dhenat qe jane per njehsim netrajten ―disajn‖ te pyetsorit dhe ka njeparaqitje te meposhtme:




―Expresion builder‖-i




FunksionetPerveq operatoreve perdorim kane edhefunksionet ,access-i ofron nje morifunksionesh qe ne vijim do ti peshkojmesipas kategorive si vijon:

Conversion(per ndryshim te formes sedates,e ne te hyjne Str(kthen numrin sistring),Val(e kthen vetem vleren numerikenga nje string p.sh nga [shprehja 1 ] kthen

1),Format(pershtat menyren e paraqitjesp.sh nga 02\03\2002 ne 2-3-2002))Date/time(punon me kohedhe date,ka ketofunksione:now,time,date,datediff)Financial (SQL)(ofron vleren mesatare dheshumen e shprehjeve ne grupe)

F k i t ( 1)




Funksionet (v-1)Financial (monetary)(ofron funksionet:NPV(serine e pageses dhesasine),DDB(cmiminfillestar,cmimin,koheqendrushmerin))

Mathematical (int(pjesa e plote e numritreale),fix(pjesa e plote e numritnegative ),sqr(rrenjezimi))

String manipulation(right(kthen numrin eparacaktuar te karaktereve ne tedjathte),len(gjatesin e stringut

),lcase(kthen shprehjen ne shkronja tevogla)) etj.

Sh hj t ( i )




Shprehjet (expression)

Pjeset e nje shprehje jane :operatoret(+,-,etj),emrat eobjekteve([adresa]),funksionet(Date(),etj),literal

values(ehene,1600,etj),constans(yes,no,etj).Nje shembull i ndertimit te nje shprehjeeshte dhene me poshte:

[data e fillimit te punes]=Date(02.03.2002)+27Shprehja e pare eshte nje rekord,e dytaeshte nje operator(=),tjetra nje

funksion(Date()),tjetra nje operator(+) dhee fundit nje ―literal‖.




Pyetsoret kushtezues

(parametrike)Roli themelore i ketyre pyetsoreve

eshte qe permes venjes se kushtevekushtezuese te marrim nje pasqyreme fleksibile te te dhenave ne ate(ato) tabela ,ndertimi i ketyre

pyetsoreve behet ne trajten―disajn‖ dhe realizohet me venjen ekushteve ne fushen ―criteria‖ netrajten e shenimit te tekstit te

mberthyer ne kllapa te mesme , sivijon [teksti] .Roli themelore iketyre pyetsoreve eshte qe tekerkohen te dhenat ne ate tabele .




Sortimi i te dhenave me ane

te pyetsoreveSortimi i te dhenave te tabeles

mund te behet edhe permespyetsoreve dhe kjo realizohetpermes zgjidhjes se fushes―sort‖

ne paraqitjen ―konstruktive ‖tepyetsorit dhe me ate rast kemi sizakonisht dy mundesi te

sortimit ate nga A-Z dhe teanasjelltin me te Z-A




Modifikimi i te dhenave ne

pyetsoreModifikimi i te dhenave ne

pyetsore mund te behet per tegjithe te dhenat e fushave teshqyrtuara apo edhe te vetem

nje fushe ,ndryshimi i te dhenavete te gjitha fushave ne pyetsorebehet me zgjedhje te opcionit―properties‖ nga ana e djathte emiut e shtypur kudo ne njehapesire te zbrazet te pyetsorit




Modifikimi i te dhenave ne

pyetsore(v-1)Ndersa modifikimi i te dhenave

sipas nje fushe behet ne menyrete njejte si me siper dukezgjedhur ―properties‖ nga ana e

djathte e mausit te vendosurmbi fushen te cilen deshirojmete ndryshojme

P Ak i




Pyetsoret Aktive

Pyetsoret aktive na mundesojnemanipulimin e te dhenave nepyetsoret e krijuar si dhe ne tabela.Kjo nenkupton se pyetsoret e tille

jane ne funksion pasi te jene krijuartabelat dhe pyetsoret e permendurme pare dhe si te tille keta nuk mund

te krijohen ne trajten themelore tetyre por vetem pasi te hapet njepyetsore tjeter ekzistues apo edhe

ndonje i ri ne trajten ―disajn‖.Dallojme disa tipe te pyetsoreveaktive




Tipet e pyetsoreve aktive

Append query

Update queryMake table query

Delete query




―Append query‖

Qellimi themelore i krijimit te

ketyre pyetsoreve eshte bartja enje grumbulli te te dhenave nga njetabele ne nje tjeter .Krijimi i tyrerealizohet me zgjedhjen e trajtes

konstruktive (disajn) te pyetsoritdhe me pas zgjedhjen e tabeles ngae cila deshirojme te bejme bartjene te dhenave ,hapi i metejme eshte

zgjedhja e opcionit ―query append ‖nga menyja ―query‖ dhe ne dialogun eparaqitur te zgjedhet baza ne tecilen deshirojme te bartiminformaten dhe tabela erkatese




Disa veti te ―Append query‖

Realizimi i tille i te dhenave do

te realizohet vetem ne atotabela ku te dhenat jane te njenatyre

Nese numri i fushave tezhvendosura eshte me i madh seai ne tabelen e zhvendosurateher ato te cilat teprojne nukdo te barten etj




―Update queries‖

Roli themelor eshte ndryshimi i te

dhenave nga nje apo edhe me shumetabela .Realizohen ne trajten ―disajn‖te pyetsoreve me opcionin―query‖dhe me pas ―update query‖.Per

kete se pari merret pyetsori netrajten ―disajn‖ me pas zgjedhentabelat dhe te dhenat te cilatdeshirojme ti ndryshojme, me ate

rast ne fushen e re ―update to‖plotesohen te dhenat qe ndrrohen

Krijimi i tabelave permes




Krijimi i tabelave permespyetsoreve (make table

query)Permes ketyre pyetsoreve

mundesohet krijimi i tabeles mete dhenat e tabelave epyetsoreve te asaj baze .Per

kete merret forma konstruktivee pyetsorit dhe zgjedhim ―query-make table query‖,me paszgjedhet baza ku deshirojme tevejme tabelen dhe emerohettabela .




―Delete query‖

Keta pyetsore na sherbejne per

fshirjen e grupeve te te dhenavenga nje apo me shume tabela .Kjorealizohet me zgjedhjen ―disajn‖ tepyetsorit dhe me pas zgjedhet

tabela(tabelat) te cilen deshirojmeme e shqyrtue me vendosje te tedhenave dhe nga menyja ―query‖zgjedhim ―delete query‖ .Veqori etyre eshte se nuk kane fushen esortimit .




Pyetsoret ―autolookup ―

Keta pyetsore krijohen me zgjedhjen eopcionit ―disajn query ‖ dhe sherbejnevetem ne ate rast kur deshirojme te

veqojme te dhena nga dy tabela te lidhurane formen nje me shume , dhe ate nefushen ―field ‖ te pyetsorit vehet fusha etabeles shume e cila e realizon lidhjen me

tabelen ame dhe me pas edhe fushat etabeles ame qe deshirojme me i pare.Meplotesim te fushes nga tabela shume e cilae realizon lidhjen plotesohen fushat tjera te

pyetsorit.(me tastin tab)




Aktivizimi i pyetsoreve

Pyetsoret aktivizohen me ane te

komandes ―run‖ , ne menyne queryte paraqitjes ―disajn‖ tepyetsorit .

Integriteti i te dhenave dhe




Integriteti i te dhenave dhe

sigurimi




Varesite funksionale




Format normalet

Bazat e orientuara kah




Bazat e orientuara kah

objektet




Bazat themelore ne mysql

Mysql eshte nje software i bazavete te dhenave me qasje te lire

(―open source‖) dhe mund temerret ne faqen :www.mysql.com

Per kete softwari ofrohet per

kliente dhe serwer ,me cka edhene secilin baze te te dhenavebehet qasja ne kete forme .




Krijimi i tabelave

Krijimi I tabeles behet me urdherat

e pershkruare si ne cdo gjuhe teSQL-se .

―Create tab1 (fusha1 tipiitedhenave,

Fusha2 tipitedhenave,Fusha3 tipiitedhenave);‖

Kjo do te ishte nje trajte themelore

e krijimit te nje tabele .

ligjeratat ne baza e te dhenave

Documents