对于没有数据的查询，除以零错误返回

Question

I'm in the process of trying to figure out a way to solve this divide by zero error. The current challenge I'm facing comes from this question I asked not too long ago.

Here's the Code I'm using that I'm plugging into reports stretching out into the end of the year:

SELECT CAST(ROUND((.01 * 2541) / Count(date_record_entered), 1) AS decimal(5,1)) 
FROM dbo.tablename
WHERE date_record_entered IS NOT NULL 
and date_record_entered >= 20131201 
AND date_record_entered <= 20131231

When it comes to current or previous months reports, there aren't any issues with the data populating. However, when the reports past the current month are accessed, I get the following error in SQL (and a similar error in C#/ASP.NET):

Msg 8134, Level 16, State 1, Line 1
Divide by zero error encountered

Here's what I've tried with no success.

Sample #1

SELECT CASE WHEN date_record_entered = 0 then null
ELSE CAST(ROUND(.01 * 2541 / COUNT(date_record_entered), 
AS deciamal (5,1)
FROM dbo.tablename 
WHERE date_record_entered IS NOT NULL 
AND date_record_entered >= 20140201 
and date_record_entered <= 20140228

Sample #2

SELECT CAST(ROUND((.01 * 2541) / NULLIF(Count(date_record_entered), 1) 
AS decimal(5,1))) 
FROM dbo.tablename 
WHERE date_record_entered IS NOT NULL 
and date_record_entered >= 20140201 
AND date_record_entered <= 20140228

Sample #3

SET ARITHABORT OFF
SET ANSI_WARNINGS OFF

SELECT CAST(ROUND(.01 * 2541 / COUNT(date_record_entered ), 1) AS decimal(5,1)) 
FROM dbo.tablename  
WHERE date_record_entered IS NOT NULL 
AND date_record_entered >= 20140201 
and date_record_entered  <= 20140228

Now this third one works in SQL but I haven't found a way to do this with a gridview/c#.

I know this may be something really simple but I'm just spinning my wheels at this point.

Answer 1

Shouldn't the second solution attempt be ...

SELECT CASE WHEN COUNT(date_record_entered) = 0 then null ELSE CAST(ROUND(.01 * 2541 / COUNT(date_record_entered), AS decimal (5,1)) END FROM dbo.tablename WHERE date_record_entered IS NOT NULL AND date_record_entered >= 140201 and date_record_entered <= 140228

With a COUNT() in the CASE WHEN

Answer 2

Sample 2 has: NULLIF(Count(date_record_entered), 1)

Instead, try: NULLIF(Count(date_record_entered), 0)

NULLIF will return the value in the first argument unless it is equal to the value in the second argument. If they are equal, NULLIF returns NULL.

SELECT CAST(ROUND((.01 * 2541) / NULLIF(Count(date_record_entered), 1), 0) AS decimal(5,1))
FROM dbo.tablename 
WHERE date_record_entered IS NOT NULL 
and date_record_entered >= 20140201 
AND date_record_entered <= 20140228

Answer 3

Using NULLIF() works because dividing by NULL returns NULL :

SELECT CAST((.01 * 2541) / NULLIF(COUNT(date_record_entered), 0) AS DECIMAL(5,1)) 
FROM dbo.tablename
WHERE date_record_entered >= 20131201 
  AND date_record_entered <= 20131231

Using CASE :

SELECT CASE WHEN COUNT(date_record_entered) = 0 THEN NULL
            ELSE CAST((.01 * 2541) / COUNT(date_record_entered) AS DECIMAL(5,1))
       END
FROM dbo.tablename 
WHERE date_record_entered >= 20140201 
  AND date_record_entered <= 20140228

Suppressing warnings can usually be avoided. date_record_entered can never be both NULL AND be between two dates, so I removed that part of the WHERE criteria.