A graphical query interface, implemented as a front-end to a relational database management system, is described. A user manipulates database schema diagrams by graphically invoking operators that specify a query. During the process of query formulation the information needed to generate an equivalent structured query language (SQL) expression is accumulated. The formal definitions of the mapping of graphical operators into SQL are given, and sample interactions between a user and the system are shown.
展开▼
