A query language is a language in which a user requests information from the database. These languages are usually on a level higher than that of a standard programming language. Query languages can be categorized as either procedural or non procedural.
In a procedural language, the user instructs the system to perform a sequence of operations on the database to compute the desired result. Ex.- PL/SQL
In a non procedural language, the user describes the desired information without giving a speciļ¬c procedure for obtaining that information. Ex.- Relational Algebra, Relational Calculus.