Formal Relational Query Language

• Relational Algebra
  • Procedural and Algebra-based
• Tuple Relational Calculus
  • Non-procedural and predicate calculus-based
• Domain Relational Calculus
  • Non-procedural and predicate calculus-based

Relational Algebra

• Created by Edgar F Codd at IBM in 1970
• Procedural language
• Six basic operators
  • Select: σ
  • Project: Π
  • Union: ∪
  • Set Difference: –
  • Cartesian Product: X
  • Rename: ρ
• Operators take one or two relations as input and generate a new relation as output

Select

Project

Union

Difference

Intersection