The Relational Calculus and Relational Algebra

In this Article we discuss the two formal languages for the relational model: first relational algebra and the second relational Calculus. The relational algebra and relational calculus were developed before the SQL language. In fact, in some ways, SQL is based on concepts from both the relational algebra and the relational calculus, as we shall see. Because most relational DBMSs use SQL as their language, the basic set of operations for the relational model is the relational algebra. These operations permit a user to specify basic retrieval requests as relational algebra expressions. At the other hand a relational calculus expression creates a new relation. In relational calculus declaration, there is no order of operations to define how to retrieve the query result-only what information the result should hold. Relational calculus based on the branch of mathematical logic called predicate calculus.