Yes, your why is correct, NULL is neither equal nor not equal to any
value. I usually nvl to return a space for null values when I have to
consider them, then a not equal will work.
At 03:43 PM 5/3/02 -0800, you wrote:
>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
>
>
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