Re: A question about performance

> CASE 1 : select *
> from subscriber ;
> (FULL TABLE SCAN)
>
> CASE 2 : select *
> from subscriber
> where subscr_id > 0 ;
> (USE INDEX)
>
> Could anyone tell me which ones performance is better , or
> they are the same ??

1. case 1 is better, because u avoid unnecessary accesses to index blocks
2. anywise, Oracle won't use the index, because u're retrieving too many rows. Are u using optimizer hints to force index usage?

3.If u're really curious what happens , execute "SET AUTOTRACE ON" from SQL Worksheet, then execute your query and take a look at the reported statistics for number of blocks/rows accessed

best wishes,

    Marin

"The important thing for all of us is never look *at* the bars, look *through* them. Because if you keep looking *at* bars, you'll never get anything done, and you'll never have fun in life, any joy."

                                                  William Wharton, "Pride"