Re: CBO choose full table scan, not index

lsllcm wrote:
> Thank you, I will do more read on it,
>
> But using index is faster than full table scan, but the cost of index
> is high full table scan.

Full table scans can be faster and more efficient than using an index. Which is better in a specific situation changes depending on many factors.

It is also important to remember that an EXPLAIN PLAN is the CBO guessing at what it will do: It is not the actual SQL PLAN used.

The only thing that matters is what Oracle actually does and that is why we have 10053 traces.

-- 
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.org