> On 4 Dec 2025, at 20:55, Rich Shepard <[email protected]> wrote:
>
> I want the script to extract only the maximum `next_contact' date and
> haven't learned how to do this from my reading of web sites.
>
> The script:
>
> select p.person_nbr, p.company_nbr, c.next_contact
> from people as p, contacts as c
> where c.next_contact >= '2025-11-01'
> group by p.person_nbr, p.company_nbr, c.next_contact
> order by p.person_nbr, p.company_nbr, max(c.next_contact);
>
> returns all contacts rather than only the latest one.
>
> Is using a sub-select the proper way?
>
> TIA,
>
> Rich
That looks like a classical case for a correlated subquery with WHERE NOT
EXISTS.
Something like:
select p.person_nbr, p.company_nbr, c.next_contact
from people as p
join contacts as c
on -- I’m really missing some kind of relation between p and c here, I think
that’s relevant
where c.next_contact >= ‘2025-11-01’
-- make sure there’s no later contact
and not exists (
select 1 -- the value is irrelevant, as long as there’s no later
instance of a contact
from contacts c2
where c2.next_contact >= ‘2025-11-01’
and c2.next_contact > c.next_contact
)
P.S. My mail-client tried to outsmart me in this reply (in no small part) and I
just got back from the pub, so I can’t exactly guarantee correctness of the
above, but the principal idea should be solid.
Alban Hertroys
--
There is always an exception to always.
