database

Question

I have some confusion plzzz help me.
i have three database tables.
table1 named phase consists two column(phaseid as pk,phase name)
table2 named sector consists three column(sector1 as pk,phase id as fk,and sector name)
table2 named user consists 6 cols(userid as pk,username, sector id, address,street, houseno)

i want such a machenism that at the front end a dropdown shows the sector name from sector table instead of showing sector id,when i select the sector name, it saves the sector id in the user table not the sector name.in short it shows sector name at the front end and saves the sector id at the back end in user table. how is it possible?????