How to get week number of the month from the date in sql server 2008

Question

In SQL Statement in microsoft sql server, there is a built-in function to get week number but it is the week of the year.

Select DatePart(week, '2012/11/30') // **returns 48** 

The returned value 48 is the week number of the year.

Instead of 48, I want to get 1, 2, 3 or 4 (week number of the month). I think the week number of the month can be achieved by modules with Month Number of this week. For e.g.

Select DATEPART(week, '2012/11/30')%MONTH('2012/11/30') 

But I want to know is there other built-in functions to get WeekNumber of the month in MS SQL SERVER.

Answer 1

Here are 2 different ways, both are assuming the week starts on monday

If you want weeks to be whole, so they belong to the month in which they start: So saturday 2012-09-01 and sunday 2012-09-02 is week 4 and monday 2012-09-03 is week 1 use this:

DECLARE @date date = '2012-09-01' SELECT (day(datediff(d,0,@date)/7*7)-1)/7+1 

If your weeks cut on monthchange so saturday 2012-09-01 and sunday 2012-09-02 is week 1 and monday 2012-09-03 is week 2 use this:

DECLARE @date date = '2012-09-01' SELECT    datediff(ww,datediff(d,0,dateadd(m,datediff(m,7,@date),0)     )/7*7,dateadd(d,-1,@date))+1 

I received an email from Gerald. He pointed out a flaw in the second method. This should be fixed now

I received an email from Ben Wilkins. He pointed out a flaw in the first method. This should be fixed now