Data processing apparatus and method

A computer operated apparatus estimates values needed by an optimiser in a database management system (DBMS). The DBMS has one or more tables for storing data, each table having zero or more columns of user-definable data types and zero or more associated user-defined routines (UDRs). The apparatus has a feature vector extractor connected to the database tables for converting the UDR inputs into a base type representation. A neural network receives the feature vector and generates estimated values which are provided to the optimiser of the DBMS. The neural network can be trained periodically using randomly generated queries, or it can be trained dynamically by capturing data generated during a query. During operation, the optimiser dynamically invokes the neural network to generate estimates such as selectivity and cost per call for determining optimum query search sequence.