multithreading - how to increase the performance of the java application fetching a large data from oracle database? -

i have 3 database tables - items, audits , comments. have fetch large amount of data items table, 1 million records, , each item fetched, have retrive data audits , comments , write report delimited file. output may ,

item entry 1     audit entry 1 item 1     audit entry 2 item 1     audit entry 3 item 1     comment entry 1 item 1     comment entry 2 item 1 item entry 2      audit entry 1 item 2     .     .     . 

now taking time, because program querying oracle 1 million times every item. increase performance thru threads i'm not familiar threads. me performance increase ?

you can write stored procedure output file utl_file package , call java. way can use like

f := utl_file.fopen('my_dir','my_file','w'); r_items in (select * items) loop   utl_file.put_line(f,r_items.name);    r_audit in (select * audit item_id = r_items.id) loop     utl_file.put_line(f,r_audit.some_field);   end loop;    r_comments in (select * comments item_id = r_items.id) loop     utl_file.put_line(f,r_comments.some_field);   end loop; end loop;