On Thu, 7 Feb 2002, Frank Joerdens wrote:
> Now I want to retrieve rows from A as in
>
> SELECT DISTINCT A.foo
> FROM A,B
> WHERE A.foo [matches some criteria]
> OR B.bar [matches some other criteria]
> AND A.id = B.a_id;
>
> This works fine if there is *at least* one row in B for each row in A.
> If there isn't, I obviously get 0 results even if the column foo in A
> matches the desired criteria. But I do want the rows from A even if
> there is no row in B that is linked to those rows in A that match the
> criteria. If the column bar in B matches the desired criteria, I also
> want the rows in A that are linked to those rows in B.
Sounds like you want a left outer join.
Maybe...
select distinct a.foo from
a left outer join b on (a.ID = b.a_id)
where a.foo [matches] or B.bar [matches]