RE: Difference between count(1) and count(*)
- From: Srinivasan Vasan <Vasan.Srinivasan@xxxxxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 9 Jul 2004 09:45:54 +0100
And if you are on 8.1.7.4, it still makes some difference if you are running
RBO as shown below:
Using Sys.Source$ for the test
Row Count using all columns
COUNT(*)
----------
1756877
Elapsed: 00:00:05.25
Row Count using a specific numbered column
COUNT(1)
----------
1756877
Elapsed: 00:00:05.50
Row Count using the pseudo-column rownum
MAX(ROWNUM)
-----------
1756877
Elapsed: 00:00:06.72
Row Count using the ROWID column
COUNT(ROWID)
------------
1756877
Elapsed: 00:00:05.67
Counting a Not-NULL column
COUNT(OBJ#)
-----------
1756877
Elapsed: 00:00:05.56
Counting a NULL column
COUNT(SOURCE)
-------------
1756877
Elapsed: 00:00:05.63
Cheers,
Vasan (x5707)
Mailpoint 28
============================================
Vasan Srinivasan * 020 8313 5707
Infrastructure Service Manager * 020 8313 5646
Oracle Technologies
Churchill Insurance, IT Department
Purple Floor, Phase 1, Churchill Court
1 Westmoreland Road,
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* Vasan.Srinivasan@xxxxxxxxxxxxx
Mobile * 07710 154 987
http://oratech
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-----Original Message-----
From: DENNIS WILLIAMS [mailto:DWILLIAMS@xxxxxxxxxxxxx]
Sent: 08 July 2004 18:09
To: 'oracle-l@xxxxxxxxxxxxx'
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@xxxxxxxxxxxxx
I said it "looked" clear - Riddick
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Michael Brown
Sent: Thursday, July 08, 2004 12:06 PM
To: oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Peter Miller
Sent: Thursday, July 08, 2004 9:40 AM
To: oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxxxxx]
Sent: 08 July 2004 12:47
To: 'oracle-l@xxxxxxxxxxxxx'
Subject: RE: Difference between count(1) and count(*)
Try the following test (using your own table instead of sys.source$ if =
you
wish) on your setup and forever dispel any myths: :-)
=20
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
=20
Cheers,=20
=20
Vasan.
-----Original Message-----
From: Jared Still [mailto:jkstill@xxxxxxxxxx]=20
Sent: 08 July 2004 08:20
To: Oracle-L Freelists
Subject: Re: Difference between count(1) and count(*)
=20
On Wed, 2004-07-07 at 23:28, Lyndon Tiu wrote:
> On Thu, 8 Jul 2004 11:27:28 +0530 oracle-l@xxxxxxxxxxxxx wrote:
> > Dear All,
> > Can you let me know the difference between count(*) and count(1) ?
>=20
> count(1) is supposed to be more efficient and faster.
=20
Notice the qualifier: 'supposed to be'
=20
Was the claim backed up by evidence?
=20
Jared
=20
=20
=20
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