How to join 2 tables on PK and FK relationship if some columns doesnt exist in one table

Hi,

I have a table which has locationNum has PK lets call it TableA and i have 2nd table Table B which has LocationNUm as Fk referecing to Table A PK.

Now, Table B has more LocationNum's than Table A and if am trying to insert its failing as some of the locationNum dont match between 2 tables.Is there any way i can get around that?

Thanks