The design and implementation of a SQL query processor and user interface for a relational database

SQL (Structured Query Language) is a relational data sublanguage developed as an external interface for System R, an experimental relational database management system developed by IBM. Because of its non-procedural nature and simple English keyword-oriented syntax, SQL can be easily learned by users of all levels of experience. In this thesis, a SQL query processor and user friendly interface are designed and implemented for use with REQUEST DBMS. REQUEST (Relational QUery SysTem)- is a relational database management system developed in the Computer Science Department of the University of Houston. The SQL query processor consists of a compiler, a high-level optimizer, and an access plan selector and interpreter. The compiler detects and reports syntatic and semantic errors to the user. The optimizer reconstructs the expression tree, produced by the compiler to minimize the cost of query execution. The interpreter traverses the expression tree and generates a sequence of calls to the underlying access method.