RE: Difference between count(1) and count(*)

Ellis,

I would have thought that if the two query plans are the same then the time taken to run the query would also be very similar.

Perhaps the myth was born around the idea that * retrieved data from the base table using rowid lookups.

Craig Munday
Software Development Manager
Giesecke & Devrient Australasia P/L, 32 Birnie Ave, Lidcombe 2141 Phone: +61 2 9646 6200 Fax: +61 2 9749 1678 Craig.Munday@au.gi-de.com http://www.gdaus.com.au

-----Original Message-----

From: Ellis R. Miller [mailto:sartre1_at_comcast.net]=20 Sent: Friday, 9 July 2004 4:47 AM
To: oracle-l_at_freelists.org
Subject: RE: Difference between count(1) and count(*)

I will alert the last dozen companies I have consulted for, immediately, as
from all indications it sounds as if they may need to stop gathering high-level requirements and move boldly into the second phase: gathering requirements for development training and mentoring i.e. Part I, Successfully unzipping the J2SE 1.4.2 SDK and, Part II, how to find it in
the file system (how do you know it really unzipped).

-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of DENNIS WILLIAMS Sent: Thursday, July 08, 2004 11:09 AM
To: 'oracle-l_at_freelists.org'
Subject: RE: Difference between count(1) and count(*)

In the first edition of Corrigan and Gurry's book Oracle Performance Tuning
(1993), which covers Version 6 (and Version 7 which was just coming out),
they state that they have conducted tests and count(*) consistently runs between 15 and 20 percent faster than count(1). So those of you still doing
new development on Version 6 will want to take note of this.

Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
I said it "looked" clear - Riddick

-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Michael Brown Sent: Thursday, July 08, 2004 12:06 PM
To: oracle-l_at_freelists.org
Subject: RE: Difference between count(1) and count(*)

If I remember what Tom Kyte said about it correctly, there was a version where it did make a difference (6, early 7 maybe) and thus a myth was born. According to Tom, the parser is now coded so that count(1) and count(*) use exactly the same code path so any differences you see between the two would occur on multiple runs of the same statement, i.e. they are caused by external events.

-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Peter Miller Sent: Thursday, July 08, 2004 9:40 AM
To: oracle-l_at_freelists.org
Subject: RE: Difference between count(1) and count(*)

1,749,951 rows returned in every case

count(rowid) - approx 3.2 secs
count(obj#)  - approx 3.5 secs
count(1)     - approx 3.6 secs
count(*)     - approx 3.6 secs
count(rownum)- approx 4.6 secs
count(source)- approx 8.6 secs

-----Original Message-----

From: Srinivasan Vasan [mailto:Vasan.Srinivasan_at_churchill.com] Sent: 08 July 2004 12:47
To: 'oracle-l_at_freelists.org'
Subject: RE: Difference between count(1) and count(*)

Try the following test (using your own table instead of sys.source$ if = =3D
you
wish) on your setup and forever dispel any myths: :-) =3D20

set trimspool on

set timing on

spool test_count.lst

Prompt Using Sys.Source$ for the test

Prompt

Prompt Row Count using all columns

select count(*) from sys.source$;

Prompt Row Count using a specific numbered column

select count(1) from sys.source$;

Prompt Row Count using the pseudo-column rownum

select max(rownum) from sys.source$;

Prompt Row Count using the ROWID column

select count(rowid) from sys.source$;

Prompt Counting a Not-NULL column

select count(obj#) from sys.source$;

Prompt Counting a NULL column

select count(source) from sys.source$;

spool off

set timing off

set trimspool off

=3D20

Cheers,=3D20

=3D20

Vasan.

-----Original Message-----

From: Jared Still [mailto:jkstill_at_cybcon.com]=3D20 Sent: 08 July 2004 08:20
To: Oracle-L Freelists
Subject: Re: Difference between count(1) and count(*)

=3D20

On Wed, 2004-07-07 at 23:28, Lyndon Tiu wrote:

> On Thu, 8 Jul 2004 11:27:28 +0530 oracle-l_at_freelists.org wrote:

> > Dear All,

> > Can you let me know the difference between count(*) and count(1) ?

>=3D20

> count(1) is supposed to be more efficient and faster.

=3D20

Notice the qualifier: 'supposed to be'

=3D20

Was the claim backed up by evidence?

=3D20

Jared

=3D20

=3D20

=3D20

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