Relational Query Languages

Database Systems 3rd Semester

Declarative and Procedural

Relational Algebra Operators

  • Select:
  • Project:
  • Union:
  • Set difference:
  • Set intersection:
  • Cartesian product:
  • Rename:

Selection of tuples (rows)

for relation r:

Selection InputSelection Output

Selection of attributes (columns)

for relation r:

Projection InputProjection Output

Joining two relations (Cartesian Product)

for relations r,s:

Cartesian Product InputCartesian Product Output

Union of two relations

for relations r, s:

Union InputUnion Output

Set difference

for relations r, s:

Set Difference InputSet Difference Output

Intersection of two relations

for relations r, s:

Intersection InputIntersection Output

Natural Join

for relations r, s:

Natural Join InputNatural Join Output