Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Mailing Lists -> Oracle-L -> RE: is it possible in pl/sql?

RE: is it possible in pl/sql?

From: Looney, Jason <Jason.Looney_at_echostar.com>
Date: Tue, 15 Feb 2005 10:16:50 -0700
Message-ID: <B8C9CF34B3F7164282C8610C93BB94AF04C63753@riv-exchb1.echostar.com>


My understanding was in the past count(*) returned a count of all non-null rows, where count(1) (or any constant) returned a count of all rows. I just verified this with 10g and this is not the case. The performance difference was to perform a full table scan, instead of counting leaf blocks in a primary key index or something like that. So maybe this was true in 6 or 7?

SQL*Plus: Release 10.1.0.2.0 - Production on Tue Feb 15 10:12:37 2005

Copyright (c) 1982, 2004, Oracle. All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Production With the Partitioning, OLAP and Data Mining options

system_at_LOCALDB> drop table test;

Table dropped.

system_at_LOCALDB> CREATE TABLE test (t1 VARCHAR2(25) NULL, t2 NUMBER NULL);

Table created.

system_at_LOCALDB>
system_at_LOCALDB> INSERT INTO test values (NULL, NULL)   2 /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> /

1 row created.

system_at_LOCALDB> select count(*) from test;

  COUNT(*)


         9

system_at_LOCALDB> select count(1) from test;

  COUNT(1)


         9

system_at_LOCALDB> select count(t1) from test;

 COUNT(T1)


         0

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Lex de Haan
Sent: Tuesday, February 15, 2005 6:01 AM To: thomas.mercadante_at_labor.state.ny.us; joelgarry_at_anabolicinc.com; oracle-l_at_freelists.org
Subject: RE: is it possible in pl/sql?

no, certainly not. count(*) and count(<any constant>) should return the same result, under all circumstances.there used to be a performance difference, in
the past.
kind regards,

Lex.  



Visit my website at http://www.naturaljoin.nl

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On
Behalf Of Mercadante, Thomas F
Sent: Tuesday, February 15, 2005 13:58
To: 'joelgarry_at_anabolicinc.com'; oracle-l_at_freelists.org Subject: RE: is it possible in pl/sql?

Does anyone know what the difference between count(*) & count(1) was *supposed* to be? Is there a theoretical functional difference?

-----Original Message-----
From: Joel Garry [mailto:joelgarry_at_anabolicinc.com] Sent: Monday, February 14, 2005 7:35 PM
To: oracle-l_at_freelists.org
Subject: Re: is it possible in pl/sql?

Anthony Wilson wrote:

>it's a myth according to the venerable Tom Kyte. The SQL engine
silently rewrites >count(1) to count(*):

Funny, he mentions that is a fact, but I've missed the reference to where the
fact is shown. Though I'm inclined to believe anything Tom says, I find this
particular one ironic in that he is talking about facts and opinions when he says it. And I'm certainly glad he mentions the differing case of 7.x, as that
means I didn't get the myth completely out of thin air or confused it with some
other function.
Just means that old habits die hard.

Joel Garry
http://www.garry.to

--
http://www.freelists.org/webpage/oracle-l
--
http://www.freelists.org/webpage/oracle-l



--
http://www.freelists.org/webpage/oracle-l
--
http://www.freelists.org/webpage/oracle-l
Received on Tue Feb 15 2005 - 12:20:40 CST

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US