Nick wrote:
messages (id, to_user, from_user, created)
1 | 1 | 2 | 2009-05-21
2 | 1 | 3 | 2009-06-21
3 | 1 | 4 | 2009-07-21
4 | 2 | 1 | 2009-05-10
5 | 2 | 3 | 2009-06-10
6 | 1 | 2 | 2009-07-10
How could I get the most recent message between two users?
Depends on what you want (all untested).
If you want the most recent message from user 1 to user 2 then:
SELECT ... where from_user=1 and to_user=2 order by created desc limit 1;
If you want the most recent message _between_ two users (either
direction), then you need to include both directions in the where clause:
where (from_user=1 and to_user=2) or (from_user=2 and to_user=1)...
If you want the most recent message time for all messages for all
user-pairs (one direction)
...to_user, from_user, max(created)...group by to_user,from_user
Or most-recent between all user-pairs:
...int4smaller(from_user,to_user), int4larger(from_user,to_user),
max(created) group by int4smaller(from_user,to_user),
int4larger(from_user,to_user)
Optimizing some of these could be "fun", though.
Cheers,
Steve
--
Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general
