RE: Difference between count(1) and count(*)
- From: "Craig Munday" <Craig.Munday@xxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 9 Jul 2004 14:06:16 +1000
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@xxxxxxxxxxxx http://www.gdaus.com.au
-----Original Message-----
From: Ellis R. Miller [mailto:sartre1@xxxxxxxxxxx]=20
Sent: Friday, 9 July 2004 4:47 AM
To: oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of DENNIS WILLIAMS
Sent: Thursday, July 08, 2004 11:09 AM
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 =
=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@xxxxxxxxxx]=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@xxxxxxxxxxxxx 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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