[Koha] Where are subject headings ( field 650$a) stored in in Koha database

Hi I imported close to 87000 items. I think I miss-align the subject column during data migration from liberty 3 to Koha, so the subjects are out of place. I would like to correct the error. I am interested in establishing which table in Koha holds subject headings and which field in particular. I will appreciate any pointers. Kind Regards, Admire Mutsikiwa ICT Projects Manager Libraries University of Zimbabwe Tel:+263-4-303276 "It is easy to dodge our responsibilities, but we cannot dodge the consequences of dodging our responsibilities." Josiah Charles Stamp, 1880-1941, former director of the Bank of England