| 摘要 |
PROBLEM TO BE SOLVED: To automatically retrieve a record which is useful to a user from a database according to the past use history of the user and to present it. SOLUTION: A storage part 209 holds conditional expressions by subsets for deciding in which subset one item value is included and and also holds cumulative frequencies by the subsets when a set of values which are possibly the values of items of a database table 200 is divided into the subsets by the items. A history registration device 205 receives a record for history update, determines in which subset of an item the item vale is included by the items of the record according to the conditional expression, and increases the value of the cumulative frequency corresponding to the subset including the item value by one. A retrieval expression automatic generation device 206 automatically generates an SQL retrieval statement while taking the cumulative frequencies, etc., by the item values recorded in the storage part 209 into consideration and presents records including item values selected frequently in the past.
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