Unary relational operations in relational algebra are operations that are applied to a single relation (table) at a time.
- These operations allow the manipulation and retrieval of specific subsets of data from a relation.
Types of unary relational operations
- Select (σ)
- Project (π)
- Rename (ρ).
1.) Select (σ)
The Select operation retrieves rows from a relation that satisfy a given condition. It filters rows based on a specified predicate and returns only those that meet the condition.
2.) Project (π)
The Project operation retrieves specific columns from a relation. It eliminates duplicate rows after selecting the specified columns, ensuring the result is a set of distinct tuples.
3.) Rename (ρ)
The Rename operation changes the name of a relation or its attributes (columns). It is useful for giving meaningful names to intermediate results or for handling queries involving multiple relations with the same attribute names.
