Re: Some Questions

ANALYZE TABLE [COMPUTE|ESTIMATE] STATISTICS will create statistics on the table in the datadictionary. This in its turn will make sure the Cost bases Optimizer is invoked instead of the Rule Based Optimizer. Rule Based Optimizer uses heuristics/rules of thumb, Cost Based Optimizer tries to calculate the exact number of buffer gets for an execution plan and will choose the execution plan with the least I/O. That said, estimate can be dangerous as it will always check the first n percent of rows in a table, which can be completely non-representative.

Final remark: Usenet is not intended as a replacement for Oracle manuals. Your questions are rather basic and well documented in the Oracle Concepts Manual, the Oracle Application Developers Guide (and for question 3) the Oracle SQL Language manual.
If you don't have those, subscribe free to http://technet.oracle.com

Hth,

Sybrand Bakker, Oracle DBA

<mihou_at_yahoo.com> wrote in message news:890t0d$tc0$1_at_nnrp1.deja.com...
> HI EVERYONE!
> CAN SOMEONE TELL ME WHAT IS THE WORTH OF:
> 1/ ANALYSE TABLE_NAME ESTIMATE STATISTICS;
>
> 2/ANALYSE TABLE_NAME COMPUTE STATISTICS;
> 3/Can I have a good example in order to understand the proper use of
> MYSEQUENCE.CURRVAL?
> 4/What do I have to do to avoid MUTATING TABLE while using a trigger.?
> (an example would be appreciated)
> 5/Does someone know a site where I can submit questions on
> Forms,Reports and PL/SQL?
>
> Thanks for your help.
>
> Mihou
>
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Wed Feb 23 2000 - 11:25:11 CST