Re: The use of COUNT(*)

From: Thomas Kyte <tkyte_at_us.oracle.com>
Date: Fri, 10 Jul 1998 18:49:43 GMT
Message-ID: <35b061c7.21415423@192.86.155.100>

A copy of this was sent to doid <doid_at_usa.net> (if that email address didn't require changing) On Fri, 10 Jul 1998 18:04:00 GMT, you wrote:

>Been there:)
>
>1) count(*) won't count nulls. this can screw up your logic
>sometimes...anyway, it's much more efficent to count( <some indexed column> )
>or count(1)
>

no thats backwards, count(*) counts nulls -- its count(<some indexed column>) -- actually count(any column) -- that won't.....

SQL> create table demo ( x int );
Table created.

SQL> create index demo_x_idx on demo(x); Index created.

SQL> insert into demo values ( null );
1 row created.

SQL> select count(*) from demo;

  COUNT(*)

---

         1

SQL> select count(x) from demo;

  COUNT(X)

---

         0

[snip]
>
>doid
>
>
>
>
>Lai King Leung wrote:
>
>> Could anyone tell me about the use of COUNT(*)?
 

Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Herndon VA  

http://govt.us.oracle.com/ -- downloadable utilities  

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Opinions are mine and do not necessarily reflect those of Oracle Corporation  

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