PURPOSE: To reduce the volume of data transfer as compared with a case for transferring the whole data to a data base device and to quickly execute data base processing by finding out a data block group including all data satisfying a condition (with an index) selected from a computer system by the use of indexes and transferring the data block group including the data group to the data base device.

CONSTITUTION: In data base processing including data selection, a part or all of data selecting conditions with indexes are combined, a group of conditions including all data 5 satisfying all applied data selecting conditions is selected and a data block group 6 including all the data satisfying the selected conditions (with indexes) is found out by the use of indexes 3 and transferred to the data base device 4.