Re: UNION: SQL-tuning

From: Jan Gelbrich <j_gelbrich_at_westfalen-blatt.de>
Date: Thu, 12 Sep 2002 09:05:03 +0200
Message-ID: <alpeh4$1rmluo$1@ID-152732.news.dfncis.de>

Hi Andrei,

did You use UNION ALL ? It is said to be better than a mere UNION.
it depends sometimes on the SELECTs, and there are many possibilities what "it" could be. Could You give an example, what You want to do ?

Jan

"Andrei Romazanov" <romazanov.andrei_at_gfos.de> schrieb im Newsbeitrag news:alpddu$1rt0js$1_at_ID-70985.news.dfncis.de...
> Hello all,
>
> I have performance-problem in a UNION.
> Normally I can separated optimize the parts from UNION,
> in this case however show both part-SELECTS good performance,
> but in UNION suddenly appears FULL TABLE SCAN. Could someone explain to
me
> this
> behavior of the Optimizer?
>
> Thank you in advance
>
> Andrei
>
>
Received on Thu Sep 12 2002 - 02:05:03 CDT