Structured query languages, such as those available for relational databases, are becoming increasingly desirable for all database management systems. Such languages are applicative: there is no need for an assignment or update statement. A new technique is described that allows for the implementation of applicative query languages against most commonly used database systems. The technique involves “lazy” evaluation and has a number of advantages over existing methods: it allows queries and functions of arbitrary complexity to be constructed; it reduces the use of secondary storage; it provides a simple control structure through which interfaces to other programs may be constructed; and the implementation, including the database interface, is quite compact. Although the technique is presented for a specific functional programming system and for a CODASYL DBMS, it is general and may be used for other query languages and database systems.

An applicative language based upon recent ideas by John Backus has been developed. The language provides a powerful formalism for the expression of complex database queries. Though currently implemented with an interface to a CODASYL system, the language employs a sufficiently general data model that use with other database management systems is possible. This paper describes the language through a number of examples and outlines its implementation.