bombadil@wanadoo.es writes:
> In my tests with views I have found a problem that can't explain.
Are those EXPLAINs really for equivalent queries? I find it very
suspicious that the estimated number of rows retrieved from "ta" is
so different in the two cases. I wonder whether you used the same
range of "fecha" in both cases.
> from t�cnico_aviso ta
> join empleado e on ta.empleado = e.cod
> join presupuesto p on ta.aviso = p.aviso
> join aviso a
> -> left join empresa em on a.empresa = em.cod
> on ta.aviso = a.n�mero;
Did you really mean to do it that way, and not as
from t�cnico_aviso ta
join empleado e on ta.empleado = e.cod
join presupuesto p on ta.aviso = p.aviso
join aviso a on ta.aviso = a.n�mero
left join empresa em on a.empresa = em.cod;
The way you wrote it forces the a-to-em left join to be done first,
which means it will generate lots of join rows that probably won't
be of any use. I suspect you want to do the left join last not first.
See
http://www.ca.postgresql.org/users-lounge/docs/7.1/postgres/explicit-joins.html
regards, tom lane
