1. A computer system comprising: a database having a database table for storing records comprising data values, the database table having first columns for storing the data values, each one of the first columns being assigned to a data field of a set of predefined data fields, and at least one second column for storing keys, each key identifying one of the records stored in the database, and a set of index tables, each index table being assigned to one of the data fields and having assigned thereto an index table identifier, means for receiving a query, the query specifying a subset of the set of data fields and a search range for each specified data field, means for storing a predetermined ordered sequence of index table identifiers, and means for processing the query by checking each one of the index tables for being relevant for the execution of the query, one of the index tables being relevant if the one of the index tables is assigned to one of the specified data fields, storing the index table identifier for each relevant index table in a query execution table, sorting the query execution table in accordance with the predetermined ordered sequence, executing the query using the index tables identified in the query execution table in the order given by the sorting of the query execution table.