Re: [SQL] order by and aggregate

[Tomasz Myrta]

Tom Lane wrote:

I don't understand what you think is wrong with this solution. It works
fine for me:

regression=# create view vv as
regression-# select max(unique1) from (select unique1 from tenk1
regression(# order by unique2) x;
CREATE VIEW
regression=# explain select * from vv;
QUERY PLAN

---------------------------------------------------------------------------------------------------
Subquery Scan vv (cost=523.00..523.00 rows=1 width=8)
-> Aggregate (cost=523.00..523.00 rows=1 width=8)
-> Subquery Scan x (cost=0.00..498.00 rows=10000 width=8)
-> Index Scan using tenk1_unique2 on tenk1 (cost=0.00..498.00 rows=10000 width=8)
(4 rows)

OK, your view is ok.

I think, you don't remember my questions about "joining views" and "sub-select with aggregate" dated on 2002-10-23, so I qoute your answer on that question (joining views):
>I think this is the same issue that Stephan identified in his response
>to your other posting ("sub-select with aggregate"). When you write
> FROM x join y using (col) WHERE x.col = const
>the WHERE-restriction is only applied to x. I'm afraid you'll need
>to write
> FROM x join y using (col) WHERE x.col = const AND y.col = const
>Ideally you should be able to write just
> FROM x join y using (col) WHERE col = const
>but I think that will be taken the same as "x.col = const" :-(

I have the same problem here, query is a bit complicated and has some_table join (subselect) X using (some_field) which doesn't work.

Regards,
Tomasz Myrta



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