⇒ The Selection Operator (σ) is an unary operator in relational algebra that performs a selection operation.
⇒ It selects tuples (or rows) that satisfy the given condition (or predicate) from a relation.
⇒ It is denoted by sigma (σ).
⇒ The condition (predicate) can use logical connectives like AND, OR, NOT, and relational operators like =, ≠, >,<, ≥, ≤ to form the selection criteria.
The WHERE clause in a SQL command corresponds to the selection operation in relational algebra.
SQL Example: SELECT * FROM Student WHERE Age > 17;
Example
To select tuples from the student table where age is greater than 17:
Relational Algebra: σage > 17 (Student)
