Patent US 4,967,341

A set of sorted columns of one table stored in a DB machine are binary-searched by a hardware in synchronism with data transfer when another table is read from a disk unit, to select a row to be joined. Where a key word sequence to be searched is stored in ascending or descending order, determination of a maximum address in an area in which key words smaller than a search key are stored and determination of a maximum address in an area in which the key words smaller than or equal to the search key are stored are parallelly executed to determine the store range in one searching.