Re: problem with update from subselect

Gary Stainburn wrote:
> Hi all, using the schema described below, I want to be able to update each
> arrival time from departure times and trip lengths.
>
> However the update fails because the subselect returns all three answers.
>
> How would I correct the update to make it work
>
> update trip set trip_arrive = (select t.trip_depart + r.route_time
> from route r, trip t where r.routeid = t.trip_route);
>

If I understand what you're trying to do correctly, this works:

test=# update trip set trip_arrive = trip_depart + r.route_time from
route r where r.routeid = trip.trip_route; UPDATE 3
test=# select * from trip;
tripid | trip_route | trip_depart | trip_arrive
--------+------------+---------------------+---------------------
1 | 1 | 2002-01-01 10:00:00 | 2002-01-01 11:40:00
2 | 1 | 2002-02-01 11:30:00 | 2002-02-01 13:10:00
3 | 2 | 2002-01-01 11:00:00 | 2002-01-01 11:30:00
(3 rows)

HTH,
Joe