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Re: sql question...

From: Raj Agarwal <rka.ra_at_worldnet.att.net>
Date: 1997/06/13
Message-ID: <01bc779c$9f141bf0$1f3874cf@rka001>#1/1

As the oracle manual explains somewhere (I think in the SQL Reference guide) -
NULL !=(or any other logical operator like =,<,etc) 'Anything'

has logical value unknown (and effectively false). Thus to get the NULL values u need to add to your #1 query:

or fellow is NULL.

Thus anytime u have null values u have to explicitly check for them use 'is NULL' or is not NULL etc.

or u can use the nvl() function to conver null values to a value: so for #1 u could use:
where nvl(fellow,'XYZ') != 'Y'

Hope this helps.

raj

-- 
Raj Agarwal
RKA Technology Inc.
81 Richland Drive,
Berkeley Hts, NJ 07922
USA
908 464 8003
FAX: 908 464 1003
rka.ra_at_worldnet.att.net

oispeggy_at_acsu.buffalo.edu wrote in article
<Pine.GSO.3.96.970612151549.25962D-100000_at_xena.acsu.buffalo.edu>...

>
> Learn something new every day....
>
> 1.
> select lname, fname This returns everyone with 'N' or 'G' or '
'.
> from resdemo None with 'Y'. None with null.
> where fellow != 'Y'
>
> 2.
> select lname, fname This returns only those with null.
> from resdemo
> where fellow is null
>
> 3.
> select lname, fname This returns only those with ' '.
> from resdemo
> where fellow = ' '
>
>
> What surprised me is that #1 did not return anyone with a null value?

> I thought it would? Why didn't it?
>
> Thanks,
>
> - Peggy -
> oispeggy_at_acsu.buffalo.edu
>
>
Received on Fri Jun 13 1997 - 00:00:00 CDT

Original text of this message

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