A formal system for manipulating relations in a database, using operators to perform queries.

• A. Relational Algebra
• B. Relational Calculus
• C. Boolean Algebra
• D. Lambda Calculus

Answer: (A)

Relational algebra is a formal system for manipulating relations in a database using operators such as select, project, join, union, intersection, and difference. It provides a procedural way to compute queries by applying these operations to input relations to produce a new relation as the result. This matches the description of using operators to perform queries on relations. The other options differ: relational calculus is declarative, specifying what result is wanted rather than how to compute it; Boolean algebra handles logic on truth values, not database relations; and Lambda calculus is a foundational model of computation focused on functions, not relational querying.