Query-by-Example (QBE) is a high-level data manipulation language that provides a convenient and unified style for querying, updating, defining, and controling a relational database. QBE is relationally complete. However, lack of subquery constructs limits the usability of QBE significantly. In this thesis, we extend QBE to support subqueries representing negation. We implement the extended QBE using the Presentation Manager and the OS/2 EE database management system. We present the grammar definition, parsing methods, and the algorithm for translating the extended QBE to SQL.
