| From: | Hannu Krosing <hannu(at)tm(dot)ee> |
|---|---|
| To: | Curt Sampson <cjs(at)cynic(dot)net> |
| Cc: | Zeugswetter Andreas SB SD <ZeugswetterA(at)spardat(dot)at>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Rules and Views |
| Date: | 2002-08-01 13:58:45 |
| Message-ID: | 1028210325.12593.5.camel@taru.tm.ee |
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| Thread: | |
| Lists: | pgsql-hackers |
On Thu, 2002-08-01 at 12:29, Curt Sampson wrote:
> On Thu, 1 Aug 2002, Zeugswetter Andreas SB SD wrote:
>
> > I had a "union all" view, which is actually a quite different animal than
> > a "union" view which needs to eliminate duplicates before further processing.
>
> I had the same problem with UNION ALL.
>
Could someone give an example where it is not safe to push the WHERE
clause down to individual parts of UNION (or UNION ALL) wher these parts
are simple (non-aggregate) queries?
I can see that it has to be made into HAVING in subquery if UNION's
subqueries are aggregate (GROUP BY) queries, but can anyone give an
example where the meaning of the query changes for non-aggregate
subqueries.
---------------
Hannu
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