Re: where clause

From: Wolfgang Breitling <breitliw_at_centrexcc.com>
Date: Fri, 06 Feb 2004 13:07:41 -0700
Message-Id: <6.0.0.22.2.20040206130553.02a231a0@pop.centrexcc.com>

NULL is NULL. It is not equal anything and it is not unequal anything. It is just NULL

To look for presence of absence of NULL you have to use the syntax especially provided for that "IS NULL" or "IS NOT NULL"

At 12:55 PM 2/6/2004, you wrote:
>Hi List,
>
>I found following results that I don't understand.
>
>SQL> desc test
>Name Null? Type
>----------------------------------------- -------- -----------------
>STATUS_FLAG CHAR(1)
>
>SQL> SELECT COUNT(*) FROM test;
>
> COUNT(*)
>----------
> 1681
>
>SQL> SELECT COUNT(*) FROM test WHERE status_flag IS NULL;
>
> COUNT(*)
>----------
> 1638
>
>SQL> SELECT COUNT(*) FROM test WHERE status_flag ='A';
>
> COUNT(*)
>----------
> 5
>
>SQL> SELECT COUNT(*) FROM test WHERE status_flag ='S';
>
> COUNT(*)
>----------
> 38
>
>SQL> SELECT COUNT(*) FROM test WHERE status_flag !='A';
>
> COUNT(*)
>----------
> 38
>
>I thought the last query should return 1676 (status_flag ='S' + status_flag
>is null) instead of 38 (status_flag ='S' only). Any ideas???
>
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Wolfgang Breitling
Oracle7, 8, 8i, 9i OCP DBA
Centrex Consulting Corporation
http://www.centrexcc.com

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Received on Fri Feb 06 2004 - 14:07:41 CST