SELECT DISTINCT acc_main_code.main_code,
acc_main_code.main_name,
acc_sub_code.sub_code,
acc_sub_code.sub_name
FROM acc_main_code,
acc_sub_code
WHERE ( acc_sub_code.co_code = acc_main_code.co_code ) and
( acc_sub_code.main_code = acc_main_code.main_code )
didn't work and the server hanging