Question

In SQL Server 2008, given a date, how would I get a date corresponding to FRI of that week?

so for example:
6/6/2012 -> 6/8/2012
6/5/2012 -> 6/8/2012

Answer 1

Assuming you want 6/9/2012 to also return 6/8/2012 (same week), this would work.
It get’s the day of week of the current date and adds the difference between that and Friday which is hardcoded to a value of 6.

SET DATEFIRST 7;    
declare @date date = '6/5/2012'

select dateadd(dd,6-datepart(dw,@date),@date) as Friday

If you want 6/9/2012 to return the next Friday, you just have to make a small modification:

SET DATEFIRST 7;
declare @date date = '6/9/2012'
set @date = dateadd(dd,1,@date) -- this adds a day to the date you inputted but doesn't matter since the function will always return to you a Friday
-- Sunday resets the week with datepart so adding a day to Saturday resets the week resulting in the next week being returned.

select dateadd(dd,6-datepart(dw,@date),@date) as Friday