Relational algebra is a mathematical foundation for relational databases, defining operations to manipulate and retrieve data.

Explanation:

Relational algebra provides fundamental operations such as:

1. Selection (σ) – Filters rows based on conditions.
2. Projection (π) – Selects specific columns.
3. Union (∪) – Combines two relations.
4. Intersection (∩) – Returns common tuples.
5. Difference (-) – Finds tuples in one relation but not in another.
6. Cartesian Product (×) – Merges two tables without conditions.
7. Join (⨝) – Combines tables based on a condition.

Example in SQL:

• Selection (σ condition(R)):

sqlCopyEditSELECT * FROM Employees WHERE department = 'HR';

• Projection (π column1, column2(R)):

sqlCopyEditSELECT name, salary FROM Employees;