Query-by-example

Query-by-Example is a query language for use by non-programmers querying a relational data base. In an earlier paper, the features of this language were introduced; however, it was assumed that the data base was already defined and available to the user.In the first part of this paper we demonstrate that the operations of Query-by-Example can be used not only to query the data base but also to define it, including data descriptions and declarations of various integrity constraints. This is an attempt to provide the user with a simplified, unified interface for a variety of functions.In the second part of this paper it is shown how one can make preliminary interrogations to retrieve a subset of the data base needed for the formulation of a specific query. This becomes very useful in cases where the data-base is very large and the user's initial task of scanning the tables for the ones relevant to his specific query becomes by itself horrendous.