select Column1 from table1 where column1 not in (select Column1 from table2)orselect Column1 from table1 where not exists (
select 1 from table2 where table2.Column1=table1.Column1)
select 1 from table2 where table2.Column1=table1.Column1)
select 1 from table2 where table2.Column1=table1.Column1)