Re: sql question...

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'

• this would give u the null values too.

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

> 

>