Computer Science CentreUniversity of Indonesia

In fo rm ationM anagem entR E S E A R C H G R O U P

Relational Database & Relational Algebra

Chapter 5,Elmasri & Navathe (2000)

In fo rm ationM anagem entR E S E A R C H G R O U P

Tuples, Domains

In fo rm ationM anagem entR E S E A R C H G R O U P

Ordering

• Usually the tuples must be ordered• It may not be ordered if the attributes

are explicit in the tuples

In fo rm ationM anagem entR E S E A R C H G R O U P

Relational Database Schema

In fo rm ationM anagem entR E S E A R C H G R O U P

Relational Database State

In fo rm ationM anagem entR E S E A R C H G R O U P

Naming of attributes

• Same names, same thing• Same names, different things• Different names, same thing

In fo rm ationM anagem entR E S E A R C H G R O U P

Entity integrity constraints

• Primary key can not be null

In fo rm ationM anagem entR E S E A R C H G R O U P

Referential Integrity Constrains

• Maintain consistency between 2 tuples relations

• Example:– Every DNO (Dept Number) on each

EMPLOYEE must match one of the actual department number

• The DNUMBER attribute of DEPARTMENT is the foreign key

In fo rm ationM anagem entR E S E A R C H G R O U P

Foreign Key

• Can also refer to its own relation• Example: SSN of Supervisor• Also called state constraints• Transition constraints?

In fo rm ationM anagem entR E S E A R C H G R O U P

Referential

In fo rm ationM anagem entR E S E A R C H G R O U P

Database update constraints• Insert:

– No null on primary key, no same primary key, no foreign key

• Delete: – when it is referred by another tuple,

you can not delete it• Update

– No foreign key

In fo rm ationM anagem entR E S E A R C H G R O U P

Relational Algebra

• Select• Project• Rename• Union,

Intersection, Difference

• Join

• Equijoin• Natural Join• Cartesian

Product• Division• Aggregate• Outer Join

In fo rm ationM anagem entR E S E A R C H G R O U P

SELECT & PROJECT

In fo rm ationM anagem entR E S E A R C H G R O U P

RENAME

In fo rm ationM anagem entR E S E A R C H G R O U P

UNION

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INTERSECT & DIFFERENCE

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CARTESIAN PRODUCT

In fo rm ationM anagem entR E S E A R C H G R O U P

JOIN

• DEPT_MGR DEPARTMENT |X|MGRSSN=SSN

EMPLOYEE

• RESULT π DNAME, LNAME, FNAME (DEPT_MGR)

In fo rm ationM anagem entR E S E A R C H G R O U P

NATURAL JOIN

• When the attribute of the tuples are the same

In fo rm ationM anagem entR E S E A R C H G R O U P

DIVISIOIN

• SMITH LNAME=‘Smith’ (EMPLOYEE)

• SMITH_PNOS πPNOS(WORKS_ON |X| ESSN=SSN SMITH)

• SSN_PNOS πESSN, PNO(WORKS_ON)

• ??? SSN_PNOS SMITH_PNOS

In fo rm ationM anagem entR E S E A R C H G R O U P

In fo rm ationM anagem entR E S E A R C H G R O U P

AGGREGATE

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LEFT OUTER JOIN

• TEMP EMPLOYEE ]X| SSN=MGRSSN DEPARTMENT

• RESULT π FNAM, MINIT, LNAME, DNAME (TEMP)