8. A computer-implemented method for performing a database query, the 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, the method comprising: receiving a query, the query specifying a subset of the set of data fields and a search range for each specified data field, and 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 a predetermined ordered sequence of index table identifiers, 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.
8. A computer-implemented method for performing a database query, the 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, the method comprising: receiving a query, the query specifying a subset of the set of data fields and a search range for each specified data field, and 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 a predetermined ordered sequence of index table identifiers, 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. 9. The computer-implemented method of claim 8 , further comprising determining the ordered sequence by determining the sizes of all index tables and sorting the index tables by size.