On Mon, 27 Aug 2001, Joseph Shraibman wrote:
> OK my query was like:
> select u.field1, ... , d.field1, ... (select ml.field from ml WHERE ml.key = u.key
>order
> by ml.keyfield desc limit 1) as lastml FROM utable u, dtable d, WHERE u.key = d.key
>and
> ... and (sublectect again) = 2;
>
> OK when I tried to convert the query:
> select u.field1, ... , d.field1, ..., mll.lastml FROM utable u, dtable d,(select
>ml.field
> as lastml from ml WHERE ml.key = u.key order by ml.keyfield desc limit 1) mll WHERE
>u.key
> = d.key and ... and lastml = 2;
>
> I got:
> ERROR: Relation 'u' does not exist
>
>
> The key fields in the subselect must match up with the key fields in the outside
>query.
> I'm afraid this would indicate that they would not match up (even if I didn't use
>short
> aliases for the tables) and the result of the subselect would be meaningless.
I think you'd want to move the entire query excepting the lastml where
condition into a single subselect in the outer from with the lastml
condition on the outside:
select * from (<old query minus lastml condition>) as blah where
lastml=2;
However, I don't think this changes the computation that it's doing
(simple example explains still show two subquery runs).
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