CSE 4701 Chapter 3-1 Chapter 3 6e & 7 5e : Relational Model – Part 1 Prof. Steven A. Demurjian,...

CSE 4701

Chapter 3-1

Chapter 3 6e & 7 5e : Relational Model – Part 1

Prof. Steven A. Demurjian, Sr. Computer Science & Engineering Department

The University of Connecticut191 Auditorium Road, Box U-155

Storrs, CT [email protected]

http://www.engr.uconn.edu/~steve(860) 486 - 4818

A large portion of these slides are being used with the permission of Dr. Ling Lui, Associate Professor, College of Computing, Georgia Tech.

The remainder of these slides have been adapted from the AWL web site for the textbook.

CSE 4701

Chapter 3-2

Data Model: The Basics Data Model

Guidelines for Logical Organization of Data Three Parts: Structure, Operations and Constraints

Structure - Ways in Which Data Logically Organized Operations - Actions on Structures

e.g., List of Objects, FIFO (Queue) or LIFO (Stack) Update Operations and Query Operations

Constraints - Logical Restrictions on Data Inherent - Implied by Logical Structure Explicit - Defined in Assertions/Integrity

Constraints Implicit - Logically Follows From the Inherent &

Explicit Constraints

CSE 4701

Chapter 3-3

Essentials of Relational Approach

The Relational Model of Data is Based on the Concept of Relations A Relation is a Mathematical Concept Based on the

Concept of Sets The Theory of Relations Provides a Formal Foundation

for the Relational Data Model The Model Was First Proposed by Dr. E.F. Codd (IBM)

in 1970 in the Paper, Entitled "A Relational Model for Large Shared Data Banks," Communications of the ACM, June 1970

CSE 4701

Chapter 3-4

R A1 A2 An......

.

.

.

Tuples

Attributesrelation name

t1t2

tm

v11 v12 v1nv21

vm1

v2n

vmn

v22

vm2

t1[An]

Relational Data Model: Data Structure

Relational Data Model Structures a Database as a Set of Relations.

A Relation Set of Tuples and Typically Shown as a Table With

Columns and Rows. Column (Field) Represents an Attribute Row (Tuple) Represents an Entity or a Relationship

CSE 4701

Chapter 3-5

Two Versions of a Student Relation

CSE 4701

Chapter 3-6

STUDENT (s#, sname, email, dept)Domain(s#): Number(9) Domain(sname): Char(30)Domain(email): Char(20) Domain(dept): Char(15)

Basic Concepts - Relation Schema

A Schema of a Relation Denoted as R(A

1:D

1, A

2:D

2 , ..., A

n:D

n)

Set of Attributes That Describe a Relation Denoted by {A

1:D

1, A

2:D

2 , ..., A

n:D

n}, where A

i (i=1, …, n)

is Attribute Name and Di is Domain Over Which A

i

is Defined Domain

The Set of Values From which the Values of an Attribute Aj are Drawn, Denoted by Domain(Aj)

Example

CSE 4701

Chapter 3-7

A Relation (Relation Instance) An Occurrence of a Relation Scheme

R( A1:D

1, A

2 :D

2 , ..., A

n :D

n);

Defined as a Subset of the Cartesian Product of the Domains that Define its Schema, Denoted by R(r) = {T1, T2, ..., Tm}

Ti (i=1,…,m) is a Member of the Cartesian Product Domain(A1) Domain(A2) … Domain(An). R is also Called the Intension of a Relation r is also Called the Extension of a Relation

Relation Instances

CSE 4701

Chapter 3-8

A Relation (Relation Instance) D

1, D

2 , D

3 , ..., D

n are Sets of Atomic Values

R( A1:D

1, A

2:D

2 , ..., A

n:D

n) is Relation Schema

A Relation of Schema R, Defined Over D1, D

2 ,

D3 , ..., D

n, is a Subset of the Set of Ordered N-tuples

{<T1, T

2, T

3, ..., T

n >| T

i D

i, i=1, ...,n};

D1, D

2 , D

3 , ..., D

n Are Called Domains

N is the Degree of the Relation (Unary, Binary, Ternary, N-ary)

Number of Tuples in R, |R|, is Cardinality of R If D

1, D

2 , D

3 , ..., D

n are Finite then there Are 2|D1||D2|

... |Dn| Possible Relation States

Relation: Formal Definition

CSE 4701

Chapter 3-9

Relation Scheme - Definition of a Relation Set of Attributes that Describe a Relation

e.g., R( A1, A

2 , ..., A

n)

Domain - Set of Values from which the Values of an Attribute Are Drawn Denoted by Domain(aj)

Relation (Relation Instance) Subset of the Cartesian Product of Domains that

Defines its Schema Occurrence of a Relation Scheme R(r) = {T1, T2, ..., Tm}.

Cardinality is the Number of Tuples

Basic Concepts

CSE 4701

Chapter 3-10

What is an Example?

R(A, B) is a Relation Schema Defined over A and B Let domain(A) = {a1, a2} and domain(B) = {0, 1, 2} Tuples are:

<a1, 0>, <a1, 2>, <a2, 2> etc. How Many Possible Tuples are there? Entire Relation is a set:

{<a1, 0>, <a1, 2>, <a2, 2> etc. }

CSE 4701

Chapter 3-11

Tuple A Row in a Relational Table e.g., ti = {vi1,vi2, ...,vin}

Attribute A Column in a Relational Table Projection of an Attribute Aj is {v1j,v2j, ...,vmj}, a

Subset of Domain(Aj.) Several Attributes may be Defined on the same

Domain (e.g., date of purchase, date of order, etc.) Null Value

Special Value Meaning “not known” or “not applicable” …

Must be a Value - Even if it is Null Degree - the Number of Attributes

Basic Concepts

CSE 4701

Chapter 3-12

EMP

PROJ

WORKS

ENO ENAME TITLE SAL

PNO PNAME BUDGET

RESPPNOENO DUR

Relation Schemes

Example EMP(ENO, ENAME, TITLE, SAL) PROJ (PNO, PNAME, BUDGET) WORKS(ENO, PNO, RESP, DUR)

Underlined Attributes are Relation Keys which Uniquely Distinguish Among Tuples (Rows)

Tabular Form

CSE 4701

Chapter 3-13

Relation Instances

ENO ENAME TITLE

E1 J. Doe Elect. Eng.E2 M. Smith Syst. Anal.E3 A. Lee Mech. Eng.E4 J. Miller ProgrammerE5 B. Casey Syst. Anal.E6 L. Chu Elect. Eng.E7 R. Davis Mech. Eng.E8 J. Jones Syst. Anal.

EMP

ENO PNO RESP

E1 P1 Manager 12

DUR

E2 P1 Analyst 24E2 P2 Analyst 6E3 P3 Consultant 10E3 P4 Engineer 48E4 P2 Programmer 18E5 P2 Manager 24E6 P4 Manager 48E7 P3 Engineer 36

E8 P3 Manager 40

WORKS

E7 P5 Engineer 23

PROJ

PNO PNAME BUDGET

P1 Instrumentation 150000

P3 CAD/CAM 250000P2 Database Develop. 135000

P4 Maintenance 310000P5 CAD/CAM 500000

PROJ[PNO] P1P2P3P4P5

EMP[TITLE]

Elect.EngSyst. AnalMech. Eng

Programmer

CSE 4701

Chapter 3-14

Examples (cont.)

Quiz: R(A, B) is a Relation Schema Defined over A and B Let domain(A) = {a1, a2} and domain(B) = {0, 1, 2} Which of the Following are Relations of R?

{(a1, 1), (a1, 2), (a2, 0)} {(a1, 0), (a1, 1), (a1, 2)}{(a1, 1), (a2, 2}, (a0, 0)}{(a1, 1), (a2, a2}, (a0, a0)}{(a1, 1, c1), (a2, 2)}

What if Attribute A is a Key?

CSE 4701

Chapter 3-15

Characteristics of Attributes

Attribute Name An Attribute Name Refers to a Position in a Tuple

by Name Rather than Position An Attribute Name Indicates the Role of a Domain

in a Relation Attribute Names must be Unique Within Relations By Using Attribute Names we can Disregard the

Ordering of Field Values in Tuples Attribute Value - Must have a Value

Must Be an Atomic Value Can Be a Null Value Meaning “Not Known”, “Not

Applicable” ...

CSE 4701

Chapter 3-16

Characteristics of Relations

No Duplicate Tuples It is a Set! The Primary Key Always Exists

No Explicit or Implicit Ordering of Tuples No Ordering of Attributes (If They Are Referred to by

Their Names) All Attribute Values Are Atomic

A Special Null Value is Used to Represent Values that are Unknown or Inapplicable to Certain Tuples

Thus - If “No” Value is Desired, “Null” is Used

CSE 4701

Chapter 3-17

Employee

A B C Da2 {b1, b2} c1 d5a2 b7 c9 d5a2 b23 c22 d1…...

A B C Da2 b2 c6 d1a2 b7 c9 d5a2 b7 c9 d5…...

R1 R2

E# Ename AGE ADDRESS

E1 Smith 30 3302 Peachtree Rd., Atlanta, GAE2 Diamond 45 1888 Buford Hyw.

E3 Evan Baker Ct. Atlanta

Examples

Are the Following Relations in a Relational Model? Why or Why Not?

CSE 4701

Chapter 3-18

Relational Schema R( A1:D

1, A

2 :D

2 , ..., A

n :D

n)

Relation R(r) With Tuples of n Columns

Denoted as Ti = {vi1,vi2, ...,vin} Attributes Aj (I=1,…,m) and R[aj] = {v1j,v2j, ...,vmj}, Domain(aj.) is a Subset of D

1, and Several Attributes

may be Defined on the Same Domain Degree N: Number of Attributes Cardinality M: Number of Tuples

Data Structure: Summary

CSE 4701

Chapter 3-19

RESERVATION

FLT# DATE CUST#

FLT-SCHEDULE

FLT#

CUSTOMER

CUST# CUST-NAMEDepT Dest ArrT

Relational Integrity Constraints

Integrity Constraints (ICs) Conditions that Must Hold on All Valid Relation

Instances at Any Given Database State Why are Integrity Constraints Needed?

What Happens when we try to Delete a Flight?

CSE 4701

Chapter 3-20

Relational Integrity Constraints Classification

There are Three Main Types of Constraints: Key Constraints Entity Integrity Constraints Referential Integrity Constraints

Other Types of Semantic Constraints: Domain Constraints Transition Constraints Set Constraints

DBMSs Handle Some But Not All Constraints Think About Programming Related Constraints

Throughout Our Upcoming Discussion

CSE 4701

Chapter 3-21

Key Constraints

Superkey (SK): Any Subset of Attributes Whose Values are

Guaranteed to Distinguish Among Tuples Candidate Key (CK):

A Superkey with a Minimal Set of Attributes (No Attribute Can Be Removed Without Destroying the Uniqueness -- Minimal Identity)

A Value of an Attribute or a Set of Attributes in a Relation That Uniquely Identifies a Tuple

There may be Multiple Candidate Keys

CSE 4701

Chapter 3-22

Key Constraints

Primary Key (PK): Choose One From Candidate Keys The Primary Key Attributed are Underlined

Foreign Key (FK): An Attribute or a Combination of Attributes (Say A)

of Relation R1 Which Occurs as the Primary Key of another Relation R2 (Defined on the Same Domain)

Allows Linkages Between Relations that are Tracked and Establish Dependencies

Useful to Capture ER Relationships

CSE 4701

Chapter 3-23

Superkeys and Candidate Keys: Examples

Example: The CAR relation schema:

CAR(State, Reg#, SerialNo, Make, Model, Year) Its primary key is {State, Reg#} It has two candidate keys

Key1 = {State, Reg#} Key2 = {SerialNo} which are also superkeys

{SerialNo, Make} is a Superkey but not a KeyWhy?

If Remove SerialNo, Make is not a Primary Key

CSE 4701

Chapter 3-24

Another Schema with Key

CAR(License#, EngineSerialNumber, Make, Model, Year)

What are Typically Used as Keys for Cars?

CSE 4701

Chapter 3-25

A Complete Schema with Keys ...

Keys Allow us to Establish Links Between Relations

What is ThisSimilar to in ER?

CSE 4701

Chapter 3-26

…and Corresponding DB Tables

Which Represent Tuples/Instances of Each Relation

1455

ASCnullWBnullnull

CSE 4701

Chapter 3-27

…with Remaining DB Tables

CSE 4701

Chapter 3-28

Superkeys vs. Candidate Keys

Superkey of R: A Superkey SK is a Set of Attributes of R Such that

No Two Tuples in Any Valid Relation Instance R(r) will Have the Same Value for SK

Given R(U), U is the Set of Attributes of R and a Relation Instance of R, Denoted As R(r), For Any Distinct Tuples T1 and T2 in R(r), T1[sk] < > T2[sk]

For Cars, Valid Superkeys Must Contain:SerialNo or State, Reg#or Both

For Students [SSN, Name, Age] Superkey but not key since removing Name, Age or Both – still SK

CSE 4701

Chapter 3-29

Superkeys vs. Candidate Keys

Candidate Key of R: One of Many Possible Keys A "Minimal" Superkey: a Candidate Key K is a

Superkey s.t. Removal of any Attribute From K Results in a Set of Attributes that is Not a Superkey

Given R(U), U is the Set of Attributes of R and a Relation Instance of R, Denoted As R(r) K is a Candidate Key If and Only If for Any A in K, There Exist Two Distinct Tuples T1 and T2 in R(r) Such That T1[k-a] = T2[k-a]

In Previous (State, Reg#, Make, Model) is SKIs it a CK? NO!Why or Why Not?

CSE 4701

Chapter 3-30

r1(PROJ)

PNO PNAME BUDGET



P14 Maintenance 450000P15 Wireless Web 350000

r2(PROJ)

PNO PNAME BUDGET




Examples

Relational Schema PROJ(PNO, PNAME, BUDGET), we Assume that PNO is the Primary Key

The Two Tables Below are Relations of PROJ Is (PNO,PNAME) a Superkey in Either? Both? Do Two Distinct Tuples have Same Value for SK? Is PNAME a Candidate Key? Explain Your Answer. Is (PNAME,BUDGET) a Superkey in Either? Both?

CSE 4701

Chapter 3-31

Relational Database Schema: A Set S of Relation Schemas (R1, R2, ..., Rn) That

Belong to the Same Database S is the Name of the Database S = {R1, R2, ..., Rn}

Entity Integrity: For Any Ri in S, Pki is the Primary Key of R Attributes in Pki Cannot Have Null Values in any

Tuple of R(ri) T[pki] < > Null for Any Tuple T in R(r)

Entity Integrity Constraint

CSE 4701

Chapter 3-32

A Constraint Involving Two Relations Used to Specify a Relationship Among Tuples in Referencing Relation and Referenced Relation

Definition: R1and R2 have a Referential Integrity

Constraint If Tuples in the Referencing Relation R1 have a Set of

Foreign Key (FK) Attributes That Reference the Primary Key PK of the Referenced Relation R2

A Tuple T1 in R1( A1, A

2 , ..., A

n) is Said to

Reference a Tuple T2 in R2 if $ FK {A1, A

2 , ...,

An} such that T1[fk] = T2[pk]

Referential Integrity Constraints

CSE 4701

Chapter 3-33

Examples

ENO ENAME TITLE

E1 J. Doe Elect. Eng.E2 M. Smith Syst. Anal.E3 A. Lee Mech. Eng.E4 J. Miller ProgrammerE5 B. Casey Syst. Anal.E6 L. Chu Elect. Eng.E7 R. Davis Mech. Eng.E8 J. Jones Syst. Anal.

EMPWORKS

PROJ

PNO PNAME BUDGET




ENO PNO RESP DUR

E1 P1 Manager 12E2 P1 Analyst 24E2 P2 Analyst 6E3 P3 Consultant 10E3 P4 Engineer 48E4 P2 Programmer 18E5 P2 Manager 24E6 P4 Manager 48E7 P3 Engineer 36

E8 P3 Manager 40E7 P5 Engineer 23

E9 P3 Engineer 30

CSE 4701

Chapter 3-34

ENO ENAME TITLE

ENO PNO RESP DUR

PNO PNAME BUDGET

WORK

EMP PROJ

WORK[ENO] is a subset of EMP[ENO]

WORK[PNO] is a subset of PROJ[PNO]

Referential Integrity Constraints

A Referential Integrity Constraint Can Be Displayed in a Relational Database Schema as a Directed Arc From R1.FK to R2.PK

CSE 4701

Chapter 3-35

Another Example: Referential Integrity

What Do theseArrows Represent

in ER Diagram?

CSE 4701

Chapter 3-36

Integrity Constraints Summary

Relational Database: Set of Relations Satisfying the Integrity Constraints

Integrity Constraints (ICs): Conditions that Must Hold on All Valid Relation Instances Key Constraints - Uniqueness of Keys Entity ICs - No Primary Key Value is Null Referential ICs Between Two Relations, Cross

References Must Point to Existing Tuples Domain ICs are Limits on the Value of Particular

Attribute Transition ICs Indicate the Way Values Changes Due

to Database Update

CSE 4701

Chapter 3-37

Operations on Relations

A DBMS Operates via User Queries to Read and Change Data in a Database

Changes Can be Inserting, Deleting, or Updating (Equivalent to a Delete followed by Insert)

One Critical Issue in DB Operations is Integrity Constraints Maintenance in the Presence of INSERTING a Tuple DELETING a Tuple UPDATING/MODIFYING a Tuple.

We’ll discuss Each case in Turn What is Constraint Maintenance Similar to in PL?

CSE 4701

Chapter 3-38

Problem Statements Integrity Constraints (ICs) Should Not Be Violated by

Update Operations To Maintain ICs, Updates may Need to be Propagated

and Cause Other Updates Automatically Common Method: Group Several Update Operations

Together As a Single Transaction If Integrity Violation, Several Actions Can Be Taken:

Cancel Operation that Caused Violation (REJECT) Perform the Operation but Inform User of Violation Trigger Additional Updates So the Violation is

Corrected (CASCADE Option, SET NULL Option) Execute a User-specified Error-Correction Routine

(Similar to What in a PL Like Java?)

CSE 4701

Chapter 3-39

Insertion Operations on Relations Insert a Duplicate Key Violates Key Integrity:

Check If Duplicates Occur Insert a Null Key Violates Entity Integrity:

Check If Null is in Any Key Insert a Tuple Whose Foreign Key Attribute Pointing to

an Non-existent Tuple Violates Referential Integrity: Check the Existence of Referred Tuple

Correction Actions: Reject the Update Correct the Violation - Change Null, Duplicate, Etc. Cascade the Access - Insert a New Tuple That Did

Not Exist/Delete Tuples that are being Referenced

CSE 4701

Chapter 3-40

Examples

ENO ENAME TITLE

E1 J. Doe Elect. Eng.E2 M. Smith Syst. Anal.E3 A. Lee Mech. Eng.E4 J. Miller ProgrammerE5 B. Casey Syst. Anal.

EMP

ENO PNO RESP

E1 P1 Manager 12

DUR

E2 P1 Analyst 24E2 P2 Analyst 6E3 P3 Consultant 10E3 P4 Engineer 48E4 P2 Programmer 18E5 P2 Manager 24

WORKS

PROJ

PNO PNAME BUDGET




E3 R. Davis Mech. Eng.?E1 Engineer 36 ?

E6 L. Chu?

E1 P5 Engineer ?E8 P3 Manager 40 ?

CSE 4701

Chapter 3-41

Deletion Operations on Relations Deleting a Tuple Referred to by Other Tuples in

Database (via FKs) would Violate Referential Integrity Action:

Check for Incoming Pointers of the Deleted Tuple. Group the Deletion and the Post-processing of the

Referencing Pointers in a Single Transaction Three Options If Deletion Causes a Violation

Reject the Deletion Attempt to Cascade (Propagate) the Deletion by

Deleting the Tuples which Reference the Tuple being or to be Deleted

Modify the Referencing Attribute Values that Cause the Violation; Each Values is Set to Null or Changed to Reference to Another Valid Tuple

CSE 4701

Chapter 3-42

Example

ENO ENAME TITLE

E1 J. Doe Elect. Eng.E2 M. Smith Syst. Anal.E3 A. Lee Mech. Eng.E4 J. Miller ProgrammerE5 B. Casey Syst. Anal.

EMP

ENO PNO RESP

E1 P1 Manager 12

DUR

E2 P1 Analyst 24E2 P2 Analyst 6E3 P3 Consultant 10E3 P5 Engineer 48E4 P2 Programmer 18E5 P2 Manager 24

P4 Manager 48

WORKS

PROJ

PNO PNAME BUDGET




E6 L. Chu Elect. Eng.

Deleting this tuple?

1. Cascading

E6

2. reference revision?E5

CSE 4701

Chapter 3-43

Modify Operations on Relations

Modify Operation Changes Values of One or More Attributes in a Tuple (or Tuples) of a Given Relation R

Maintaining ICs Requires to Check If the Modifying Attributes Are Primary Key or Foreign Keys.

Integrity Check Actions: Case 1:

If the Attributes to be Modified are Neither a Primary Key nor a Foreign Key, Modify Causes No Problems

Must Check and Confirm that the New Value is of Correct Data Type and Domain

Case 2: Modifying a Primary Key Value Similar to Deleting One

Tuple and Insert Another in its Place

CSE 4701

Chapter 3-44

The Types of Constraints That Most DBMSs Maintain are Key Constraints Entity Constraints Referential Integrity

Constraints

Other Semantic Constraints Need to Be Maintained by Application Developers/programmers Transition Constraints Domain Constraints Etc.

Three Types of Update Operations: INSERT, DELETE, MODIFY

Constraint Maintenance During Updates

Some DB Do Maintain Domain Constraints via Enumeration and Value-Range Data Types

Constraints and Update Operations

CSE 4701

Chapter 3-45

Summary of Model: Common Terms

Informal Table Column Row (Instance) Table Definition Populated Table

Formal Relation Attribute Tuple Schema of Relation Extension

CSE 4701

Chapter 3-46

Interpretation Linguistic Logical Logical

Schema

Tuple

declaration assertion predicate

fact instance of assertion

values of satisfying predicate

Theoretical Foundation

Notion of Relation and Tuple is Modeled as in Set Theory

Changes From Set Theory Existence of Null Value in the Tuples Most Implementation Allow Duplicate Tuples in

Result Sets (such as Projection) Interpretation of Relations:

CSE 4701

Chapter 3-47

Features of Relational Model

Simple and Mathematically Elegant Simple, Uniform Data Structure Solid Theoretical Foundation

Advantage of the Relational Model: Simplicity Separation Between Data and Data Access Easier to Define Data and Data Structure Easier to Write Queries (Specify What Not How) Relational DBMS can do More for You

PC-Based Systems have Brought DB to Masses MS Access - Easy to Use Integration with Office Tools (Word, Excel)

CSE 4701

Chapter 3-48

Relational DBMS Products Popular Commercial Products:

ORACLE SYBASE INFORMIX INGRES SQL Server MySQL

Popular Java-based RDB Products InstanceDB and Simple Text

Popular Personal DBMS product MSFT/Access

Mobile Apps MySQL Lite

CSE 4701

Chapter 3-49

Quiz

R(A, B) is a Relation Schema Defined Over A and B Let Domain(A) = {a1, a2} and Domain(B) = {0, 1, 2} Is R(A, B) Equivalent to R(B, A)? How Many Possible Relations That the Schema R

May Have? Is the Set {(a1, 1), (a2, 2}, (a0, 0)} a Relation of

Schema R? What is the Degree of a Relation of Schema R? What is the Cardinality of the Following Relation

{(a1, 1), (a1, 2), (a2, 0)} of Schema R?

Yes

2 23 =2 6 = 64

No

2

3

CSE 4701

Chapter 3-50

Relational Languages

A Relational Language Defines Operations to Manipulate Relations Used to Specify Retrieval Requests (Queries) Query Result is Expressed in the Form of a Relation

Classification Relational Algebra (A Quick First Look) Relational Calculus (Jump to Chapter XX) Basic Structured Query Language (SQL) Back to Relational Algebra (Back to Chapter YY) Advanced Structured Query Language (SQL)

CSE 4701

Chapter 3-51

Basic Relational Operations: Unary Operations

SELECT s PROJECT or P.

Binary Operations Set operations:

UNION INTERSECTION DIFFERENCE –

CARTESIAN PRODUCT JOIN operations

What is Relational Algebra?

Relational Algebra is a Procedural ParadigmYou Need to Tell What/How to Construct the Result

Consists of a Set of Operators Which, When Applied to Relations, Yield Relations (Closed Algebra)

CSE 4701

Chapter 3-52

Relational Algebra

R S unionR S intersectionR \ S set differenceR S Cartesian

product

A1, A2, ..., An (R) projection

F (R) selection

R S natural join

R S theta-joinRS division[A1 B1,.., An Bn] rename

CSE 4701

Chapter 3-53

ENO ENAME TITLE

E1 J. Doe Elect. EngE6 L. Chu Elect. Eng.

TITLE='Elect. Eng.'(EMP)ENO ENAME TITLE

E1 J. Doe Elect. Eng.

E2 M. Smith Syst. Anal.

E3 A. Lee Mech. Eng.

E4 J. Miller Programmer

E5 B. Casey Syst. Anal.


E7 R. Davis Mech. Eng.

E8 J. Jones Syst. Anal.

EMP

TITLE='Elect. Eng.’ OR TITLE=‘Mech.Eng’(EMP)

Selection Example

CSE 4701

Chapter 3-54

Another Selection Example

ASCnullWBnullnull

CSE 4701

Chapter 3-55

Projection Example

PNO,BUDGET(PROJ)

PNO BUDGET

P1 150000

P2 135000

P3 250000

P4 310000

P5 500000

PROJ

PNO BUDGET

P2 135000

P3 250000

P4 310000P5 500000

PNAME

P1 150000Instrumentation

Database Develop.

CAD/CAM

MaintenanceCAD/CAM

CSE 4701

Chapter 3-56

Other Projection Examples

CSE 4701

Chapter 3-57

Relational Algebra Expression Several Operations can be Combined to form a

Relational Algebra Expression (query) Example: Retrieve all Customers over age 60?

Method 1: CNAME, ADDRESS, AGE (s AGE>60(CUSTOMER) )

Method 2: Senior-CUST(C#, Addr, Age)

= CNAME, ADDRESS, AGE (s AGE>60(CUSTOMER) ) Method 3: CNAME, ADDRESS, AGE (C) where

C = s AGE>60(CUSTOMER)

CSE 4701

Chapter 3-58

ENO ENAME TITLE









EMP TITLE(PROJ)

Elect.EngSyst.AnalMec.EngProgrammer

TITLE

Characteristics of Projection The PROJECT Operation Eliminates Duplicate Tuples

in the Resulting Relation Why? Projection Must Maintain a Mathematical Set (No

Duplicate Elements)

CSE 4701

Chapter 3-59

Selection with Projection Example

CSE 4701

Chapter 3-60

Union, Difference, Intersection Examples

What are these OtherThree Result Tables?

CSE 4701

Chapter 3-61

Cartesian Product: Example

A B C

a1a2a3

b1b1b4

c3c5c7

FE

f1f5

e1e2

A B C E

a1a1a2a2a3a3

b1b1b1b1b4b4

c3c3c5c5c7c7

e1e2e1e2e1e2

R S

R S F

f1f5f1f5f1f5

CSE 4701

Chapter 3-62

Cartesian Product Example

ENO ENAME EMP.TITLE SAL.TITLE SAL





Elect. Eng. 40000

Syst. Anal. 34000

Mech. Eng. 27000

Programmer 24000





Elect. Eng. 40000

Syst. Anal. 34000

Mech. Eng. 27000

Programmer 24000

Elect. Eng. 40000

Syst. Anal. 34000

Mech. Eng. 27000

Programmer 24000

Elect. Eng. 40000

Syst. Anal. 34000

Mech. Eng. 27000

Programmer 24000









EMP SAL

ENO ENAME TITLE

E1 J. Doe Elect. Eng








EMP

TITLE SAL

SAL

Elect. Eng. 40000

Syst. Anal. 34000

Mech. Eng. 27000

Programmer 24000

CSE 4701

Chapter 3-63

-Join Example

ENO ENAME TITLE









EMP

TITLE SAL

SAL

Elect. Eng. 40000

Syst. Anal. 34000

Mech. Eng. 27000

Programmer 24000

ENO ENAME

E1 J. Doe

M. SmithE2

E3 A. Lee

E4 J. Miller

E5 B. Casey

E6 L. Chu

E7 R. DavisE8 J. Jones

TITLE

Elect. Eng.

Analyst

Mech. Eng.

Programmer

Syst. Anal.

Elect. Eng.

Mech. Eng.Syst. Anal.

SAL

40000

34000

27000

24000

34000

40000

2700034000

EMP E.TITLE=SAL.TITLE SAL

SAL.TITLE

Elect. Eng.

Analyst

Mech. Eng.

Programmer

Syst. Anal.

Elect. Eng.

Mech. Eng.Syst. Anal.

CSE 4701

Chapter 3-64

Examples

A B C

a1a2a3

b1b1b4

c3c5c7

B E

b1b5

e1e2

R S

R R.B=S.B S

A R.B

a1a2

b1b1

C E

c3c5

e1e1

S.B

b1b1

EQUIJOIN

A R.B C E

a1a2

b1b1

c3c5

e1e1

R SNatural Join

CSE 4701

Chapter 3-65

Natural Join Example

ENO ENAME TITLE









EMP

TITLE SAL

SAL

Elect. Eng. 70000

Syst. Anal. 80000

Mech. Eng. 56000

Programmer 60000

ENO ENAME E.TITLE SAL

E1 J. Doe Elect. Eng. 70000

E2 M. Smith Syst. Anal. 80000

56000

80000



EMP SAL

60000E4 J. Miller Programmer

80000E5 B.Casey Syst.Anal

70000E6 L. Chu Elect.Eng

56000E7 R.Davis Mech.Eng

CSE 4701

Chapter 3-66

Another Natural Join Example

CSE 4701

Chapter 3-67

Yet Another Natural Join Example

1455

CSE 4701

Chapter 3-68

Concluding Remarks

What have we Seen in Chapter 3? Basic Concepts of Relational Model Including

Relation/Table, Tuple/Row, Attribute/Column, Domain/Attribute Value

Concept of SK, CK, PK, and FK for Identification and Referential Integrity

Integrity Constraints as they Relate to Referential Dependencies Check for Modification Operations

Overall, Relational Theory is Basis for SQL, Normal Forms, ER-Relational Translation, etc.

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CSE 4701 Chapter 3-1 Chapter 3 6e & 7 5e : Relational Model – Part 1 Prof. Steven A. Demurjian,...

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