Re: count(rowid) vs count(*)

From: Roger Jackson <rjackson_at_wire.net.au>
Date: Tue, 13 Jul 1999 20:39:43 +1000
Message-ID: <7mf5oc$t63$1@caley.wire.net.au>

Andy,

I would agree with you. I've actually also found that the Oracle DBA Certification Exam Guide, written by Oracle Press also specifies that you should use count(rowid) or count(1) instead of count(*).

But it really doesn't explain why.

It looks like I will have to do the tests myself.

Andy Marden <amarden_at_altavista.net> wrote in message news:3789E2C0.F05EB6E6_at_altavista.net...
> Tests that I ran - a while back now, must be on 7.1 I guess, showed
> this to be untrue, and that count(*) performed better than count(1).
> Maybe this has been optimised (it would make sense wouldn't it?)
>
> Andy
>
> Roger Jackson wrote:
> >
> > Hi,
> >
> > I was reading an article just recently which stipulated that you should
not
> > use count(*) to determine the number of rows in a table, but use
count(1) or
> > count(ROWID) instead. These options are faster because they bypass some
> > unnecessary operations in Oracle's SQL processing mechanism.
> >
> > Can somebody explain to me why this would be faster and what mechanisms
are
> > bypassed.
> >
> > TIA
> >
> > Roger
Received on Tue Jul 13 1999 - 05:39:43 CDT