How to calculate the number of “Tuesdays” between two dates in TSQL?

Question

I\'m trying to figure out how to calculate the number of \"Tuesdays\" between two dates in TSQL?

\"Tuesday\"could be any value.

Answer 1

declare @from datetime= '9/20/2011' 
declare @to datetime  = '9/28/2011' 

select datediff(day, -6, @to)/7-datediff(day, -5, @from)/7

1. find the week of the first monday before the tuesday in @from.
2. find the week of the first monday after @to
3. subtract the weeks