Relational Calculus is a Non-procedural Query Language which uses mathematical predicate calculus instead of algebra. Relational calculus doesn’t work on mathematics fundamentals such as algebra, differential, integration, etc. That’s why it is also known as predicate calculus.

There is two type of relational calculus:

Tuple relational calculus
Domain relational calculus

Relational calculus is a theoretical framework within relational database management systems (RDBMS) used to describe queries declaratively. It’s a non-procedural language that focuses on what data to retrieve rather than how to retrieve it. There are two main types of relational calculus:

Tuple Relational Calculus (TRC): In TRC, you specify what data you want to retrieve by defining a formula that describes the desired tuples. It operates on sets of tuples satisfying the formula.
Domain Relational Calculus (DRC): DRC, on the other hand, focuses on describing the desired results using formulas involving domains of attributes. It specifies the constraints for the variables in the formula, and the system finds the tuples that satisfy these constraints.

Both TRC and DRC provide a way to formulate queries in a way that’s independent of the underlying physical storage and implementation details of the database, allowing for a more abstract and mathematical approach to querying data.