| 摘要 |
PURPOSE:To evade the rearrangement of a record item and the duplication of this item by defining substitue keys for optional plural items within a desired record. CONSTITUTION:A substitute key control information memory area 12 stores the information on the compounded items in case a substitute key consists of said items. For instance, the area 12 stores the number of discontinuous items included in the substitute key, the position information, the length, etc. A substitude key defining part 13 refers to each record of a master file 10 for substitute keys of designated items. Then the part 13 extracts all records containing the contents of the substitute key for each said contents and sets the pointer information to produce a substitute index file 11. When plural items are designated, the record is retrieved by the contents combining these plural imtes. Then the control information is stored to the area 12 for automatic renewal of the file 11 when the corresponding record is extracted or the record is added to or deleted from the file 10.
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