Re: Q: Performance

Hi,

>From: martinj_at_pi.net
 

>Because of daily usage of large tables, I have some performance questions I'd
 

>like answers to:
 

>1. What's faster:
>-----------------
>A. select rownum from A where A.field1 NOT IN
> (select fieldA from B)
>B. select rownum from A where NOT EXISTS
> (select 'x' from B where A.field1 = B.fieldA)
>C. Anything else

Hard to tell, use tkprof.

>2. Are there performance differences between:
>---------------------------------------------
>A. Select count(*) ...
>B. Select count(rownum) ...
>C. Select count('x') ....

I don't think so.

>3. What's faster:
>-----------------
>A. Insert into ... values (....) as select ...
>B. Insert with a cursor

method A may eat up your rollback segment spaces.                                                                          

William.
william.lee_at_cwolhk.com
___
* UniQWK #5138* Received on Mon Jun 05 1995 - 00:00:00 CEST