METHOD AND APPARATUS FOR ACCESSING DATA FROM DATA ATTRIBUTES TABLES

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. The population densities of tables described above characterize a typical system even though the range of each accessing key is selected to provide for more extrmeme systems which have much larger numbers of tables of data attributes and, larger numbers of more densely populated intermediate tables. Advantageously, such an arrangement sharply reduces the amount of storage required to store data in typical systems while retaining the flexibility of permitting different accessing keys to have widely varying numbers of values in different systems.