PURPOSE:To shorten a processing time by constituting the above system so that when a record of a second table is read successively to each record of a first table, first of all, read-in is executed successively from the head record, and at a second time and thereafter, read-in is executed from the direction being reverse to the previous time. CONSTITUTION:An inequality condition coupling means 3 reads in successively records of a first and a second tables from a data base 9 constructed on a secondary storage device 8, and compares the value of a first column of the record of the first table and the value of a second column of the record of the second table. Subsequently, a pair of records being unequal are outputted, and also, when the record of a second table is read in successively to each record of the first table, first of all, read-in is executed in order from the head record, and at a second time and thereafter, read-in is executed from the direction being reverse to the previous time. In such a way, the possibility that a page containing a record to be read in is stored in a buffer 7 is enhanced remarkably, the number of times of input and output processings to a secondary storage device is decreased and the processing time can be shortened remarkably.
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