How to get week number from date in SQL Server?

Question

How to get week number from date, if first date is Friday (interval week is Friday - Thursday)?

My query:

declare @week as int
set @week='04'

SELECT datepart(WEEK,DATEADD(DAY,-5,Day))  Week,DAY

FROM [MyTable]
where datepart(WEEK,DATEADD(DAY,-5,Day)) =@week

but the result is wrong.

how to get result like this:

Note: 29 Dec is in 2017

Answer 1

The first day of the week is based on the language settings of the server. The default setting is US English 7 (Sunday). But you can easily change it by using DATEFIRST . Put this line at the top of your query:

SET DATEFIRST 5;