create table TableA (UniqueID int identity(1,1), RationCArdid int, MemID int, NAme varchar(MAx), Primary Key(UniqueID))
create table TableB (UniquID2 int identity(1,1), RationCArdid int, MemID int, NAme varchar(MAx), Primary Key(UniquID2))
insert into tableA values(1,1,'a'),(2,2,'b'),(3,3,'c')
insert into tableB values(1,1,'a'),(2,2,'b'),(3,3,'c'),(4,4,'d'),(5,5,'f')
select B.RationCArdid from tableB B where B.RationCArdid not in (select RationCArdid from tableA)