COUPLING CONDITION SELECTING SYSTEM FOR RELATION TYPE DATA BASE SYSTEM

摘要

PURPOSE:To decrease on an average the number of records of a table immediately after coupling and to reduce the subsequent processing type by selecting a coupling column candidate whose unique exponent is large as a coupling column. CONSTITUTION:A coupling condition selecting device 1 sets a correction constant, a coupling condition candidate, a limiting condition before coupling and unique information as an input parameter 2, derives a unique exponent with regard to each coupling condition candidate, and outputs the coupling condition candidate in which said exponent becomes maximum as an optimum coupling condition 3. In such a case, in the device 1, a control part 10 controls an operation of a unique exponent calculating part 20 and a K value information generating part 40 and executes a selection of an optimum coupling condition. The calculating part 20 executes a calculation of a unique exponents of a designated column. A unique processing part 60 derives a contribution to a reference of each unique. The generating part 40 derives a prescribed value to all columns appearing in unique information by using a tree structure analyzing part 50.