Re: Difference between count(1) and count(*)
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 9 Jul 2004 22:14:36 +0100
And that is, of course, a rather important point;
because Oracle almost invariably recognises a
call to 'count the rows in the table' however you
disguise it, and does whatever the CBO thinks
is the fastest row count.
Even to the extent where you can do
something like the following:
create table t1(col1 number primary key, col2 number not null, col3
number);
insert lots of data.
create bitmap index t1_b3 on t1(col3);
select count(col1) from t1;
and get an execution plan which is:
index fast full scan on t1_b3.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/seminar.html
Optimising Oracle Seminar - schedule updated May 1st
----- Original Message -----
From: "Powell, Mark D" <mark.powell@xxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Friday, July 09, 2004 3:48 PM
Subject: RE: Difference between count(1) and count(*)
At last someone who bothered to post explain plans to show that the
comparisons were valid tests!
----------------------------------------------------------------
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:
