Question

I have to calculate date before two days based on the condition .

Example date = ‘2012-09-01’ then @date should be ‘2012-08-30’ but here if 2012-08-31 is not working day then @date should be ‘2012-08-29’.

Could you please help me on this

Answer 1

Your question though apparently seems to be simple, but not so as there are many test cases involved in it (at least I have interpreted in that way). Let me first write the query (I assume you are using Sql Server 2005+)

Declare @tbl_Data Table(Dates Date,WorkDayCount Int)

Insert Into @tbl_Data Select '2012-08-25',1
Insert Into @tbl_Data Select '2012-08-26',1
Insert Into @tbl_Data Select '2012-08-27',1
Insert Into @tbl_Data Select '2012-08-28',1
Insert Into @tbl_Data Select '2012-08-29',1
Insert Into @tbl_Data Select '2012-08-30',1
Insert Into @tbl_Data Select '2012-08-31',0
Insert Into @tbl_Data Select '2012-09-01',1

Declare @InputData Date = '2012-09-01'

;WITH CTE AS
(
    SELECT Sequence = ROW_NUMBER() OVER(ORDER BY Dates DESC),*
    FROM @tbl_Data
    WHERE  Dates < @InputData
)
,CTE2 AS
(
    SELECT 
        Sequence = ROW_NUMBER() OVER(ORDER BY Dates DESC)
        ,Dates 
        ,WorkDayCount
    FROM
    (
        SELECT * FROM CTE WHERE Sequence  = ((SELECT TOP 1 Sequence FROM CTE WHERE WorkDayCount = 1)-1)
        UNION  
        SELECT TOP 2 * FROM CTE WHERE WorkDayCount = 1
    )X
)
SELECT TOP 1
            Date = CASE WHEN  Sequence = 1 AND  WorkDayCount = 0 THEN (SELECT Dates FROM CTE2 WHERE  Sequence = 3)
                    WHEN  Sequence = 1 AND  WorkDayCount = 1 THEN (SELECT Dates FROM CTE2 WHERE  Sequence = 2)
            END 
FROM CTE2

CASE 1:Input date is 1st Sept(2012-09-01) and the immediate previous date’s WorkDayCount = 0

Result: 2012-08-29

Reason: Since August 31st’s WorkDayCount = 0, so the working date will be 29th August

CASE 2: Input date is 1st Sept(2012-09-01) and the August 31st + August 30th WorkCount = 0.

Result: 2012-08-28

CASE 3:Input date is 1st Sept(2012-09-01) and the immediate previous date’s WorkDayCount = 1

Result: 2012-08-30

Kindly correct me if any of the assumptions/test cases are incorrect.

Let me know your concern.