Retrieving the record not matched with a join. - Mailing list pgsql-sql

Hi,

I have two tables, A and B.  A contains records which includes an ID or one
of the records in table B.

A would typically contain the fields:

IDA
IDB
DATA1
DATA2

and B:

IDB
DATA3
DATA4

I have several records in both but a few of the records in A has a IDB field
which does not point to a valid record in B (the record has been deleted).

I know how to get all the records in A that have existing records in B.
SELECT * FROM A, B WHERE A.BID = B.BID.

Now my question ... How do I get the records in A that DO NOT have existing
records in B ???

Perplexed look and deep frown ;-)

Thanks in Advance
Frans