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The Relational Data Model

1 Asst.Prof. Intiraporn Mulasastra

Data Modeling

Real World

Data Recordings

Data Modeling Data Representation

Data Items

<e,a,v>

<e,a,v>

<e,a,v>

แบบจ ำลองขอ้มูล ขอ้มูลในเคร่ืองคอมฯ

ER-Model

Relational Data Model

2 Asst.Prof. Intiraporn Mulasastra

Relational Database

is a collection of tables

3 Asst.Prof. Intiraporn Mulasastra

Tables

Heading: table name and column names

Body: rows, occurrences of data

StdSSN StdLastName StdMajor StdClass StdGPA

123-45-6789 WELLS IS FR 3.00

124-56-7890 NORBERT FIN JR 2.70

234-56-7890 KENDALL ACCT JR 3.50

Student Table

รหสั นำมสกุล ภำควิชำ ชั้นปี เกรดเฉล่ีย

ไม่มีการเกบ็ข้อมูลซ า้ซ้อน

4 Asst.Prof. Intiraporn Mulasastra

Physical storage

Row1 Row2 Row3 ….

Data in Table

Column names, type

Table Scheme in data dictionary tables

5 Asst.Prof. Intiraporn Mulasastra

E-R Model Relational Model

E-R Model

Entity type

Entity Instance

Relationship

Attribute

Primary key required

Relational Model

Table

Row

Entity References by

using keys

Column

Some tables may not

have a primary key**

Foreign key*

6 Asst.Prof. Intiraporn Mulasastra

Alternative Terminology

Table-

oriented

Set-oriented Record-

oriented

Table Relation Record-type,

File

Row Tuple Record

Column Attribute Field

A tuple : (‘John’, ‘CPE’, 3.1)

7 Asst.Prof. Intiraporn Mulasastra

Primary keys

Entity integrity

Each table has column(s) with unique values

Ensures entities are traceable

StdSSN StdLastName StdMajor StdClass StdGPA

123-45-6789 WELLS IS FR 3.00

124-56-7890 NORBERT FIN JR 2.70

234-56-7890 KENDALL ACCT JR 3.50

PK

unique 8 Asst.Prof. Intiraporn Mulasastra

Types of Relationship

Do not support many to many

one to one

one to many, many to one

9 Asst.Prof. Intiraporn Mulasastra

Relationships 1:N

CourseNo

CrsDesc

CrsUnits

Course

OfferNo

OffLocation

OffTime

Offering

Has

OfferNo OffLocation OffTime CourseNo

111 CPE 203 1/2014 204351

222 CPE 204 2/2014 204351

333 CPE 204 2/2014 204111

CourseNo CrsDesc CrsUnits

204351 Database 3

204111 Programming 3

Different OfferNo, the same CourseNo

Add PK of Course table in Offering table

10 Asst.Prof. Intiraporn Mulasastra

Foreign Keys (FK)

OfferNo OffLocation OffTime CourseNo

111 CPE 203 1/2014 204351

222 CPE 204 2/2014 204351

333 CPE 204 2/2014 204111

CourseNo CrsDesc CrsUnits

204351 Database 3

204111 Programming 3

foreign key

Referential integrity

Values of FK must match values from a source table

Ensures valid references among tables

Course Offering

11 Asst.Prof. Intiraporn Mulasastra

enroll

Many to Many Relationship

12 Asst.Prof. Intiraporn Mulasastra

M-N Relationships

Rows of each table are related to

multiple rows of the other table

Not directly represented in the

relational model

We need

two 1-M relationships and

an associative table

13 Asst.Prof. Intiraporn Mulasastra

Relationships N:M

StdSSN

StdName

Student

OfferNo

OffLocation

Offering

EnrGrade

EnrollmentRegisters Grants

associative table

14 Asst.Prof. Intiraporn Mulasastra

enroll

Many to Many Relationship

StdSSN

StdName

Student

OfferNo

OffLocation

Offering

EnrGrade

EnrollmentRegisters Grants

transform

1:N N:1

N:M

15 Asst.Prof. Intiraporn Mulasastra

OfferNo CourseNo

1234 IS320

4321 IS320

Offering

StdSSN OfferNo

123-45-6789 1234

234-56-7890 1234

123-45-6789 4321

124-56-7890 4321

Enrollment

StdSSN StdLastName

123-45-6789 WELLS

124-56-7890 KENDALL

234-56-7890 NORBERT

Student

Many to Many Relationship

16 Asst.Prof. Intiraporn Mulasastra

Formal Definitions I

Superkey: column(s) with unique values

Candidate key: minimal superkey

A B C D 1 41 500 m 1 42 600 n 2 42 600 o 3 43 750 p

AB, AC, D

?

BC?

17 Asst.Prof. Intiraporn Mulasastra

Formal Definitions I

Primary key: a designated candidate key; cannot contain null values

Foreign key: column(s) whose values must match the values in a primary key of a referenced table

NULL value: special value meaning value unknown or inapplicable

18 Asst.Prof. Intiraporn Mulasastra

Formal Definitions II

Entity integrity

No two rows with the same primary key value

No null values in a primary key

Referential integrity

Foreign keys must match candidate key of source table

Foreign keys in some cases can be null

19 Asst.Prof. Intiraporn Mulasastra

Enrollment Table Example

OfferNo StdSSN EnrGrade

INTEGER CHAR(11) DECIMAL(3,2)

PRIMARY KEY

foreign key foreign key

OfferNo Student

StdSSN Offering

PRIMARY KEY PRIMARY KEY

20 Asst.Prof. Intiraporn Mulasastra

CourseNo

CrsDesc

CrsUnits

Course

OfferNo

OffLocation

OffTime

Offering

Has

teach

ONE

ONE

MANY

MANY

21 Asst.Prof. Intiraporn Mulasastra

Offering Table Example

OfferNo CourseNo ……… FacSSN

PRIMARY KEY

foreign key1 foreign key2

CourseNo Course

FacSSN Faculty

PRIMARY KEY PRIMARY KEY

22 Asst.Prof. Intiraporn Mulasastra

Self-Referencing Relationships

Foreign key that references the same

table

Represents relationships among

members of the same set

Not common but important when

occurring

23 Asst.Prof. Intiraporn Mulasastra

Hierarchical Data Display

098-76-5432

Leonard Vince

876-54-3210

Christopher Colan

654-32-1098

Leonard Fibon

543-21-0987

Victoria Emmanual

Supervice

Supervice

24 Asst.Prof. Intiraporn Mulasastra

Faculty Data

FacSSN FacFirstName FacLastName FacRank FacSalary FacSupervisor

098-76-5432 LEONARD VINCE ASST $35,000 654-32-1098

543-21-0987 VICTORIA EMMANUEL PROF $120,000

654-32-1098 LEONARD FIBON ASSC $70,000 543-21-0987

765-43-2109 NICKI MACON PROF $65,000

876-54-3210 CRISTOPHER COLAN ASST $40,000 654-32-1098

987-65-4321 JULIA MILLS ASSC $75,000 765-43-2109

FK refers to the same table

25 Asst.Prof. Intiraporn Mulasastra

Generalization Hierarchy Example

CASCADE DELETE for Foreign Keys

Table Attribute PK FK

Employee EmpNo, EmpName, EmpHireDate

EmpNo

-

SalaryEmp EmpNo, EmpSalary EmpNo

EmpNo

Hourly Emp EmpNo, EmpRate EmpNo

EmpNo

26 Asst.Prof. Intiraporn Mulasastra

Relationship Window with 1-M

Relationships

Student

Offering

Enrollment

Faculty

Faculty1

Course

MANY

27 Asst.Prof. Intiraporn Mulasastra

Referenced Rows

Referenced row

Foreign keys reference rows in the associated primary key table

Enrollment rows refer to Student and Offering

Actions on referenced rows

Delete a referenced row

Change the primary key of a referenced row

Referential integrity should not be violated

28 Asst.Prof. Intiraporn Mulasastra

Offering Table

OfferNo CourseNo ……… FacSSN

1 204351

PRIMARY KEY foreign key

CourseNo CourseName CourseUnit

204351 Database Systems 3

Course PRIMARY

KEY

foreign key

1. If 204351 is deleted

2. What will happen with OfferNo 1?

29 Asst.Prof. Intiraporn Mulasastra

Possible Actions on referenced rows

Restrict: do not permit action on the

referenced row

Cascade: perform action on related

rows e.g., deletion or Nullify: set foreign key of related row

to NULL only valid if foreign keys accept null

values

Default: set foreign keys to a default value

Ex. Course

Ex. Offering

30 Asst.Prof. Intiraporn Mulasastra

Data Retrieval

Relational Database

31 Asst.Prof. Intiraporn Mulasastra

Relational Algebra Overview

Table operators

Transform one or two tables into a new

table

Understand operators in isolation

Input, calculation, output

Classification

Table specific operators

Traditional set operators (,,)

Advanced operators

32 Asst.Prof. Intiraporn Mulasastra

1.Subset Operators

Restrict Project

Select columns

Select

rows

33 Asst.Prof. Intiraporn Mulasastra

Subset Operator Notes

Restrict (Select Data)

Logical expression as input

Example: OffDays = 'MW' AND OffTerm = 'SPRING' AND OffYear = 2003

Project

List of columns is input

Duplicate rows eliminated if present

Often used together

34 Asst.Prof. Intiraporn Mulasastra

2.Extended Cross Product

Builds a table consisting of all

combinations of rows from each of the

two input tables

Cross Product Table A, Table B

Table C

A

B

11

22 X

A 11

A 22

B 11

B 22 35 Asst.Prof. Intiraporn Mulasastra

Extended Cross Product Example

FacSSN

111-11-1111

222-22-2222

333-33-3333

FacSSN StdSSN

111-11-1111 111-11-1111

111-11-1111 444-44-4444

111-11-1111 555-55-5555

222-22-2222 111-11-1111

222-22-2222 444-44-4444

222-22-2222 555-55-5555

333-33-3333 111-11-1111

333-33-3333 444-44-4444

333-33-3333 555-55-5555

Faculty

Student

Faculty PRODUCT Student

StdSSN

111-11-1111

444-44-4444

555-55-5555

36 Asst.Prof. Intiraporn Mulasastra

3.Join Operator

Most databases have many tables

Combine tables using the join operator

Specify matching condition

Can be any comparison but usually =

PK = FK most common join condition

37 Asst.Prof. Intiraporn Mulasastra

Natural Join Example

FacSSN FacName

111-11-1111 joe

222-22-2222 sue

333-33-3333 sara

OfferNo FacSSN

1111 111-11-1111

2222 222-22-2222

3333 111-11-1111

FacSSN FacName OfferNo

111-11-1111 joe 1111

222-22-2222 sue 2222

111-11-1111 joe 3333

Faculty

Offering

Natural Join of Offering and

Faculty

Relationship diagram

Join condition:

Faculty.FacSSN = Offering.FacSSN

38 Asst.Prof. Intiraporn Mulasastra

4.Outer Join Overview

Join excludes non matching rows

Preserving non matching rows is

important in some problems

Outer join variations

Full outer join

One-sided outer join

Left

right

39 Asst.Prof. Intiraporn Mulasastra

3.Right Outer Join

4 of Outer Join Operators

1.Left Outer Join 2.Join

Matched rows

using the join

condition

Keep unmatched

rows of the left

table + (2)

Keep unmatched

rows of the right

table + (2)

4.Full outer join

40 Asst.Prof. Intiraporn Mulasastra

Left outer join

Builds a table consisting of all matched

rows of the two input tables

Keep unmatched rows of the left table too

Table A

ID Name

A xx

B yy

No ID

11 A

22 A

33 -

join ID Name No

A xx 11

A xx 22

B yy -

Table B matched

unmatched 41 Asst.Prof. Intiraporn Mulasastra

Left Outer Join

Faculty

FacSSN FacName

111-11-1111 JOE

222-22-2222 SUE

333-33-3333 SARA

Offering

OfferNo FacSSN

1111 111-11-1111

2222 222-22-2222

3333 111-11-1111

4444 -

Offering Left Join Faculty

OfferNo FacSSN FacName

1111 111-11-1111 JOE

2222 222-22-2222 SUE

3333 111-11-1111 JOE

4444 **Non matching row**

Non matching row

42 Asst.Prof. Intiraporn Mulasastra

Full Outer Join Example

FacSSN FacName

111-11-1111 joe

222-22-2222 sue

333-33-3333 sara

Offerno FacSSN

1111 111-11-1111

2222 222-22-2222

3333 111-11-1111

4444

FacSSN FacName OfferNo

111-11-1111 joe 1111

222-22-2222 sue 2222

111-11-1111 joe 3333

333-33-3333 sara

4444

Faculty

Offering

Outer Join of Offering and Faculty

matched

Unmatched L

Unmatched R

43 Asst.Prof. Intiraporn Mulasastra

Traditional Set Operators

A UNION B

A INTERSECT B

A MINUS B

A B 44 Asst.Prof. Intiraporn Mulasastra

Union Compatibility

Requirement for the traditional set

operators

Strong requirement

Same number of columns

Each corresponding column is compatible

Positional correspondence

Apply to similar tables by removing

columns first

45 Asst.Prof. Intiraporn Mulasastra

Summarize Operator

Decision-making operator

Compress groups of rows into calculated

values

Simple statistical (aggregate) functions

Not part of original relational algebra

46 Asst.Prof. Intiraporn Mulasastra

Summarize Example

StdSSN AVG(EnrGrade)

111-11-1111 3.4

222-22-2222 3.3

333-33-3333 3.0

StdSSN OfferNo EnrGrade

111-11-1111 1111 3.8

111-11-1111 2222 3.0

111-11-1111 3333 3.4

222-22-2222 1111 3.5

222-22-2222 3333 3.1

333-33-3333 1111 3.0

EnrollmentSUMMARIZE Enrollment

ADD AVG(EnrGrade)

GROUP BY StdSSN

47 Asst.Prof. Intiraporn Mulasastra

Divide Operator

Match on a subset of values

Suppliers who supply all parts

Faculty who teach every IS course

Specialized operator

Typically applied to associative tables

representing M-N relationships

48 Asst.Prof. Intiraporn Mulasastra

Division Example

SuppNo PartNo

s3 p1

s3 p2

s3 p3

s0 p1

s1 p2

PartNo

p1

p2

SuppNo

s3

SuppPart Part SuppPart DIVIDEBY Part

s3 {p1, p2, p3}

contains {p1, p2}

ตวัอย่างเช่น ลูกค้าคนใดซ้ือ นม และขนมปังด้วยในใบเสร็จเดยีวกนั

49 Asst.Prof. Intiraporn Mulasastra

Relational Algebra Summary Operator Meaning

Restrict (Select) Extracts rows that satisfy a specified condition

Project Extracts specified columns.

Product Builds a table from two tables consisting of all possible combinations

of rows, one from each of the two tables.

Union Builds a table consisting of all rows appearing in either of two tables

Intersect Builds a table consisting of all rows appearing in both of two specified

tables

Difference Builds a table consisting of all rows appearing in the first table but not

in the second table

Join Extracts rows from a product of two tables such that two input rows

contributing to any output row satisfy some specified condition.

Outer Join Extracts the matching rows (the join part) of two tables and the

“unmatched” rows from both tables.

Divide Builds a table consisting of all values of one column of a binary (2

column) table that match (in the other column) all values in a unary (1

column) table.

Summarize Organizes a table on specified grouping columns. Specified aggregate

computations are made on each value of the grouping columns.

50 Asst.Prof. Intiraporn Mulasastra

Summary

Relational model is commercially

dominant

Learn relations, primary keys and

foreign keys,

Learn to represent data relationships

Understand concept of data operations

51 Asst.Prof. Intiraporn Mulasastra