Question

Hello SOF community:

I have a table like this

 InvoicingActivityStartDay InvoicingActivityEndDay
 27                        26
 27                        26
 01                        NULL --NULL MEANS LAST DAY OF MONTH
 01                        NULL
 15                        14    

I need a T-SQL query that will return the following for the data above, given the current date; if current date = 12-JAN-2012, the results should be as below

InvoicingActivityStartDATE               InvoicingActivityEndDATE
27-DEC-2011 12:00:00.000                 26-JAN-2012 23:59:99.999
27-DEC-2011 12:00:00.000                 26-JAN-2012 23:59:99.999
01-DEC-2011 12:00:00.000                 31-DEC-2011 23:59:99.999
01-DEC-2011 12:00:00.000                 31-DEC-2011 23:59:99.999
15-DEC-2011 12:00:00.000                 14-JAN-2012 23:59:99.999

Can you please show me how this be done in a single query?

Please note that if the start day is 1, that means the end day is always the last day of the previous month.

Answer 1

If I interpret your requirements correctly (that the start day is that day of last month, and the end day is that day of this month; except when start day is 1), then you may want something like this (assuming your start/end days are integers; if not, cast them as ints):

SELECT DATEADD(DAY,InvoicingActivityStartDay-1,
                DATEADD(Month,DATEDIFF(Month,0,GETDATE())-1,0))
       AS [InvoicingActivityStartDATE] 
      ,CASE InvoicingActivityStartDay
      WHEN 1 THEN DATEADD(ms,-3,
                     DATEADD(Month,DATEDIFF(Month,0,GETDATE()),0))
      ELSE DATEADD(ms,-3,
            DATEADD(DAY,InvoicingActivityEndDay,
                    DATEADD(Month,DATEDIFF(Month,0,GETDATE()),0)))
      END AS [InvoicingActivityEndDATE] 
FROM t