Abstract: The present invention discloses a join operation processing system in a relational model where a data base processing mechanism provides at least maximum/minimum calculation execution means, reduction sort execution means and the join operation execution means.During the join operation for generating a new table linking tuples of a plurality of pertinent tables based on a common field or plurality of common fields, a minimum extraction range for determining the tuples to be processed is determined with respect to the join field or the plurality of join fields for each table which is considered as the object of the join. The operation rate is thereby improved by omitting the processing referring to unwanted data.