Abstract: A method and apparatus for accessing data in a data base that provides for a minimum of unused storage while preserving easy expandability. A group of accessing keys are used to identify the attributes data that is being sought in a data base. In accordance with the invention, subkeys are extracted from members of the group of data accessing keys and these subkeys are advantageously rearranged to form derived accessing keys. Subkeys are densely populataed if most values of a subkey are used in most systems. One of the derived accessing keys, derived from densely populated subkeys is used for accessing the tables of data attributes that are therefore advantageously densely populated. Another derived accessing key, derived from sparsely populated subkeys, is used for accessing a sparsely populated head table. Derived keys of intermediate population density are used for accessing tables intermediate between the head tables and the tables of data attributes.