Re: Avoid multiple scan of the same table
From: DA Morgan <damorgan_at_psoug.org>
Date: Thu, 21 Aug 2008 16:08:31 -0700
Message-ID: <1219360101.251144@bubbleator.drizzle.com>
Date: Thu, 21 Aug 2008 16:08:31 -0700
Message-ID: <1219360101.251144@bubbleator.drizzle.com>
maks71_at_gmail.com wrote:
> Is there way to avoid multiple scan of the same table in following?
>
> Select c1 as v1, c2 as v2, c3 as v3
> From t1
> Union
> Select c1 as v1, c2 as v2, c4 as v3
> From t1
> Where c5 < 5000
>
>
> The output should look like..
>
> v1, v2, v3
> v11, v21, v31
> v12, v22, v32
> and so on.
>
> Rows from the both queries can be same so UNION is required to avoid
> duplicates in current construct.
One way would be to use a WITH CLAUSE query. http://www.psoug.org/reference/with.html
-- Daniel A. Morgan Oracle Ace Director & Instructor University of Washington damorgan_at_x.washington.edu (replace x with u to respond) Puget Sound Oracle Users Group www.psoug.orgReceived on Thu Aug 21 2008 - 18:08:31 CDT