Introduction to Relational Calculus

by K. Yue

1. Introduction

• Non-procedural, declarative and higher level.
• Two kinds:
  • Domain Oriented Relational Calculus
• Tuple Oriented Relational Calculus
• Results specified by the set builder form.

2. TORC

• The variables in TORC are tuples.
• Format: {t | condition(t)}
• Reference to individual attribute A of tuple t: t(A) or t.A.
• Membership: R(t): t is a tuple in the relation R.
• Boolean operations: AND, OR, NOT.
• Quantifiers: universal and existential.

Exercise:

Work on some of the query questions listed in the Supplies database example in TORC.

3. DORC

• The variables in DORC are attributes (domain values).
• Query By Example (QBE) is based on DORC.

Exercise:

Work on some of the query questions listed in the Supplies database example in DORC.