RE: IN() question

Roy,

that is correct! null is null and cannot be compared to anything including itself.
well, it can be compared to itself, but it never equals itself.

Tom Mercadante
Oracle Certified Professional

-----Original Message-----
Sent: Monday, May 06, 2002 12:54 PM
To: Multiple recipients of list ORACLE-L

Does this mean that you can't include Null as a value in an IN() clause? That is, would something like:

> SQL> SELECT COUNT(*)
> 2 from leisure_plan_master_temp
> 3 where membership_class = 'D'
> 4 AND pay_METHOD IN (Null, 'C','P');

count rows where pay_METHOD is Null? (Disregarding for the moment the problem Lisa was actually trying to solve.)

Thanks!

-Roy

Roy Pardee
Programmer/Analyst
SWFPAC Lockheed Martin IT
Extension 8487

-----Original Message-----
Sent: Friday, May 03, 2002 5:33 PM
To: Multiple recipients of list ORACLE-L

In any equivalence operation (which includes non-equivalence, too), NULL never returns TRUE -- it just returns NULL which non-TRUE has the same result as FALSE. Only IS and IS NOT operators can be used to evaluate NULLs...

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Friday, May 03, 2002 5:43 PM

> Slap me if this is a dumb question.
>
> Here's my pay methods
>
> SQL> SELECT ASCII(PAY_METHOD), PAY_METHOD, COUNT(*)
> 2 FROM LEISURE_PLAN_MASTER_TEMP
> 3 WHERE MEMBERSHIP_CLASS = 'D'
> 4 GROUP BY PAY_METHOD;
>
> ASCII(PAY_METHOD) P COUNT(*)
> ----------------- - ----------
> 67 C 42955
> 80 P 34373
> 11786
>
> I expected this statement to return the 11,786 records that have null
> values. However, it doesn't:
>
> SQL> SELECT COUNT(*)
> 2 from leisure_plan_master_temp
> 3 where membership_class = 'D'
> 4 AND pay_METHOD NOT IN ('C','P');
>
> COUNT(*)
> ----------
> 0
>
> But when I do this, I get the answer I expect.
>
> SQL> SELECT COUNT(*)
> 2 from leisure_plan_master_temp
> 3 where membership_class = 'D'
> 4 AND PAY_METHOD IS NULL;
>
> COUNT(*)
> ----------
> 11786
>
> This isn't exactly correct. There may be other values in this field, and
if
> they show up I need to include them, not just records where this field is
> null. What am I missing? Is it because the value is NULL that Oracle
> excludes it from the IN() statement, because of the classic definition of
> NULL (can't be defined, therefore can't be sure it's not a C or a P)?
>
> This is easy enough to fix, I'll change my data load to populate the null
> values with my own code. But still? Have I got the WHY correct?
>
> Thanks for any light someone can shed on this stupid question.
>
> Lisa Koivu
> Oracle Database Monkey Mama
> Fairfield Resorts, Inc.
> 5259 Coconut Creek Parkway
> Ft. Lauderdale, FL, USA 33063
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Koivu, Lisa
> INET: lisa.koivu_at_efairfield.com
>
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