Re: Question about Append hint in Insert
- From: Daniel Fink <Daniel.Fink@xxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 21 Jun 2004 12:55:28 -0600
One other 'subtle' difference in this scenario is that you cannot
perform an INDEX UNIQUE SCAN on the index when you are using an equality
predicate. IIRC, the CBO will cost the allowable RANGE SCAN the same as
the UNIQUE SCAN so there should not be differences in query plan
selection nor execution time. If you are using explain plan/tkprof, etc.
you will see a drastic difference in the card(inality) estimate, but
this does not really factor in to the equation (in this case).
Also, to keep things clear and supportable, make sure to document the
reason for doing this.
Regards,
Daniel
jaromir nemec wrote:
> Hi Lex,
>
> Thanks for the correction of my misinterpretation.
> Does it mean there are no other differences or things to keep in mind when
> deciding between unique and non-unique index to support unique constraint?
>
> Thanks
> Jaromir D.B.Nemec
>
>
>
>>one small correction: non-unique indexes do *not* allocate more space...
>
>
>
>
>
> ----------------------------------------------------------------
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> ----------------------------------------------------------------
> To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
> put 'unsubscribe' in the subject line.
> --
> Archives are at //www.freelists.org/archives/oracle-l/
> FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
> -----------------------------------------------------------------
----------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
----------------------------------------------------------------
To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
put 'unsubscribe' in the subject line.
--
Archives are at //www.freelists.org/archives/oracle-l/
FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------
Other related posts:
