On Thursday, December 4, 2025, Rich Shepard <
rshepard@appl-ecosys.com> wrote:
On Thu, 4 Dec 2025, David G. Johnston wrote:
I would go with a lateral join subquery of the contracts table. Using an
aggregates to perform ranking is an anti-pattern. You want the contract
ranked first when ordered by contract_date. Either use a window function
to explicitly rank the contracts or use a limit/fetch clause to simply
return the first ordered one.
David,
I'm closer, but still missing the proper syntax:
select p.person_nbr, p.company_nbr, c.next_contact
from people as p, contacts as c
join lateral (select max(c.next_contact) as last_contact
where p.person_nbr = c.person_nbr and
last_contact >= '2025-11-01'
)
c on true;
resulting in:
psql:companies-contacted-2025.sql:9: ERROR: aggregate functions are not allowed in FROM clause of their own query level
LINE 3: join lateral (select max(c.next_contact) as last_contact
As mentioned, the aggregate max should be avoided - you aren’t doing statistics, you are ranking.
Select person.*, lastcontact.* from person join lateral (select contact.* from contact where contact.person_id=person.person_id order by last_contact_date desc limit 1) as lastcontact on true;
David J.
