module this data processing system 9 executes the desired processings by fetching the data as required from the table memory 11 0 and index memory 11 1 into the local memory and stores the data as required within each memory 11 0 or 11 1 the data base processing mechanism 12 includes at least the join operation controller 14 and interpretation execution system 15 the join operation controller 14 executes processings such as indentifing the type of join predicates described by users the determination of the join processing sequence and the selection of access path etc and and additionally controls the processings of the interpretation execution system 15 moreover the interpretation execution system 15 comprises the reduction sort execution system 16 join operation execution system 17 and the maximum minimum calculation execution system 21 and has a function of interpreting the instructions issued by users and of executing the corresponding processings the maximum minimum calculation execution system module 21 provides the function of preliminarily judging the tuple extraction range for the join object table as explained later by referring to fig3 from the join predicate described by the user given for the join processing and the dictionary information for the index to be used the reduction sort execution system module 16 executes as explained later by referring to fig3 the sort for the unsorted tables and those other tables which cannot use the index while limiting the extraction range of relations required for the join processing moreover the join operation execution system module 17 uses the sorted tables and index extracts the tuples within extraction range in the finally limited form and executes the join processing instructed by users fig3 shows an embodiment indicating the processings in the data base processing mechanism of fig2.