SQL DATEPART(dw,date) need monday = 1 and sunday = 7

This will do it.

SET DATEFIRST 1;

-- YOUR QUERY

Examples

-- Sunday is first day of week
set datefirst 7; 
select DATEPART(dw,getdate()) as weekday


-- Monday is first day of week
set datefirst 1;
select DATEPART(dw,getdate()) as weekday

You can use a formula like:

(weekday + 5) % 7 + 1

If you decide to use this, it would be worth running through some examples to convince yourself that it actually does what you want.

addition: for not to be affected by the DATEFIRST variable (it could be set to any value between 1 and 7) the real formula is :

(weekday  + @@DATEFIRST + 5) % 7 + 1

You can tell SQL Server to use Monday as the start of the week using DATEFIRST like this:

SET DATEFIRST 1