1. Objectives
After completing this session, you will be able to:
– Define Relational Calculus
– Distinguish between Relational Algebra and Relational Calculus.
– Explain Tuple Relational Calculus and write queries.
– Explain Domain Relational Calculus and write queries.
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2. Introduction
• Relational Calculus is a non-procedural query language. A
calculus expression specifies “what to retrieve” rather than
“how to retrieve”. This makes relational calculus different
from relational algebra.
• A calculus expression may be written in different ways, but the
way it is written has no bearing on how a query should be
evaluated.
• In relational calculus, a query is solved by defining a solution
relation in a single step.
• Relational calculus is mainly based on the well-known
propositional calculus, which is a method of calculating with
sentences or declarations. That's why it is also known as
declarative language
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3. Relational calculus Types
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Various types of relational calculus are:
Tuple Relational Calculus (TRC)
Domain Relational Calculus (DRC)
4. Relational Algebra Vs Relational Calculus
• Relational Algebra, RA, is a
Procedural language.
• RA means “how to
obtain the result”.
The order
in which
• In RA,
specified
operations
performed.
have to
• RA is independent on
domain.
a
• RA is nearer to
programming language.
• Relational Calculus, RC, is
non-procedural language.
• RC means “What to obtain”
as result.
is • In RC, The order is not
the specified.
be
• RC can be a domain
dependent.
• RC is not nearer to
programming language.
