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Conditioning in the WHERE clause

Posted on 2006-07-02
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Last Modified: 2008-03-04
Hello.

Let say I have a date field and it can be NULL. I query this table in my store procedure and depending on the parameter, I want to select either all values WITH NULL and WITHOUT NULL, only values WITH NULL,  or only values WITHOUT NULLS.

I tried to put CASE and IF into my WHERE clause but apparently it's either not supposed to be working there or I had a wrong syntax. Anyway, my preudo-script is:

SELECT * FROM my_table
WHERE
CASE @UseNulls
   WHEN 1 THEN ( my_date IS NULL )
   WHEN 0 THEN ( my_date IS NOT NULL )
   WHEN 2 THEN ?? /* to have both */ ??

END

Thanks,
Mik

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Question by:Yurich
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5 Comments
 
LVL 12

Accepted Solution

by:
Einstine98 earned 300 total points
ID: 17027908
SELECT * FROM my_table
WHERE
(My_Date IS NULL AND @UseNulls = 1)
OR (My_Date IS NOT NULL AND @UseNulls = 0)
OR @UseNulls = 2

Case does work, but not the way you used it...

 SELECT * FROM my_table
WHERE
CASE
          WHEN My_Date IS NULL THEN 'YES'
          ELSE 'NO'
     END = CASE @UseNulls
   WHEN 1 THEN 'Yes'
   WHEN 0 THEN 'No'
END
OR @UseNulls = 2
0
 
LVL 12

Expert Comment

by:Einstine98
ID: 17027962
Hey... just had another though (which I always do :-) )

SELECT * FROM my_table
WHERE
CASE
      WHEN My_Date IS NULL THEN '1'
        ELSE '0'
END = @UseNulls
OR @UseNulls = 2
0
 
LVL 17

Assisted Solution

by:HuyBD
HuyBD earned 100 total points
ID: 17029407
Try this.

SELECT * FROM my_table
WHERE
NULLIF(my_date,'NIL') =
CASE @UseNulls
   WHEN 1 THEN 'NIL'
   WHEN 0 THEN  my_date
   WHEN 2 THEN NULLIF(my_date,'NIL')
END

Hope this help
0
 
LVL 75

Assisted Solution

by:Anthony Perkins
Anthony Perkins earned 100 total points
ID: 17030717
SELECT      *
FROM      my_table
WHERE       @UseNulls = 1 And my_date IS NULL
      Or @UseNulls = 0 And my_date IS NOT NULL
      Or @UseNulls = 2

Or if you prefer to read it this way:

SELECT      *
FROM      my_table
WHERE       (@UseNulls = 1 And my_date IS NULL)
      Or (@UseNulls = 0 And my_date IS NOT NULL)
      Or (@UseNulls = 2)
0
 
LVL 21

Author Comment

by:Yurich
ID: 17034239
thank you guys,

case ... = case ... is especially interesting as I didn't know you can do it like that

regards,
yurich
0

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