SQL Help

I have two tables with identical layouts, 3 columns each. One contains rows
I want to delete in the other.

Say
Table A (order number, orderitem number, copy char(12)); 20000 rows Table B( order number, orderitem number, copy char(12)); 4000 rows

The three columns are part of a composite primary key.. I would like to delete the rows in A that are present in table B.. One way to do this
is
delete from A where
order||orderitem||copy in (select order||orderitem||copy from B);

That works fine.. but I was wondering if there was a way to do it without
a string concatenation..

If I try something like
delete from A
where exists (select 1 from A x, B y
where x.order = y.order and x.orderitem = y.orderitem and x.copy = y.copy)

it deletes all rows...
What to do with subquery if you have to match 3 columns instead of 1?

Thanks
Dc. Received on Tue Jul 11 2000 - 00:00:00 CDT