Relational Algebra
• Relational algebra is a widely used procedural query language.
• It collects instances of relations as input and gives occurrences of
relations as output.
• It uses various operations to perform this action.
• Relational algebra operations are performed recursively on a relation.
• The output of these operations is a new relation, which might be
formed from one or more input relations.
Fundamental Operations in Relational Algebra
1. Selection Operator (σ)
• The SELECT operation is used for selecting a subset of the tuples
according to a given selection condition.
• Sigma (σ) symbol denotes it.
• It is used as an expression to choose tuples which meet the selection
condition.
• Select operation selects tuples that satisfy a given predicate.
2. Projection Operator (П)
• The projection eliminates all attributes of the input relation except
those mentioned in the projection list.
• The projection method defines a relation that contains a vertical
subset of a Relation.
• This helps to extract the values of specified attributes and eliminates
duplicate values.
• (П) is the symbol used to choose attributes from a relation.
• This operation helps you to keep specific columns from a relation and
discards the other columns.
