Question

I have a date field in a query and I do want to get GROUP BY report like this:

DATE    COUNT
2010-01  10
2010-02  2
...
2010-12  24
2012-13  34

What is the proper syntax to obtain this on SQL Server?

Answer 1

All these conversions to string work, but I find this method more efficient, albeit less readable:

SELECT m = DATEADD(MONTH, DATEDIFF(MONTH, 0, [DATE]), 0), COUNT(*)
  FROM dbo.TheTable
  GROUP BY DATEADD(MONTH, DATEDIFF(MONTH, 0, [DATE]), 0); 

If you don’t want to repeat the expression, then:

;WITH x AS (SELECT m = DATEADD(MONTH, DATEDIFF(MONTH, 0, [DATE]), 0)
  FROM dbo.TheTable)
SELECT m, COUNT(*)
  FROM x GROUP BY m;

This way the output is still a date/time value and can be used that way for other things. And it doesn’t involve any messy string conversions.