Table-formatted data is divided into information blocks, each including a value list where item values are arranged in order of item value number corresponding to the item value of each item, and a pointer array where pointer values, each indicate an item value number, are arranged in order of unique record number. A part of records is selected as a subset, and in response to the selection, an ordered set array including the record numbers of the subset is created. Each record number in the ordered set array indicates the position of one of the pointer values in the pointer array, which are arranged in the item value number array correspondingly to positions where the record numbers are arrayed. With reference to values in the item value number array, a second pointer array wherein position elements are arranged, and a second value list wherein value elements are arranged, are generated.