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
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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)
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