Oracle-L: IN() question

From: Koivu, Lisa <lisa.koivu_at_efairfield.com>
Date: Fri, 03 May 2002 15:43:38 -0800
Message-ID: <F001.00457D3E.20020503154338@fatcity.com>

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(*)

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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Author: Koivu, Lisa
INET: lisa.koivu_at_efairfield.com

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