SQL Server 获取日期是星期周几(默认从周日开始到周六 1-7)

ALTER FUNCTION  [dbo].[GetWeekDay]
(
@Year INT, @Month INT ,@Day INT
)
RETURNS INT
AS
BEGIN

 DECLARE @date DATETIME= DATEFROMPARTS(@Year,@Month,@Day);
 DECLARE @weekday INT =0;
 --select @@datefirst
 --SELECT alias, * from master..syslanguages
 --SELECT DATEPART(WEEKDAY,'2018-11-17')
 IF @@DATEFIRST =7---从周日开始到周六  1,2,3,4,5,6,7
 BEGIN
 SET @weekday= 7-(8- DATEPART(WEEKDAY,@date) )%7  ;
 END ELSE  -----1---从周一开始到周日  1,2,3,4,5,6,7
 BEGIN
 SET @weekday= DATEPART(WEEKDAY,@date) ;
 END
--SELECT 7-(8- DATEPART(WEEKDAY,'2018-11-23') )%7
--SELECT 7-(8- DATEPART(WEEKDAY,'2018-11-24') )%7
--SELECT 7-(8- DATEPART(WEEKDAY,'2018-11-25') )%7
--SELECT dbo.GetWeekDay(2018,11,23)
--SELECT dbo.GetWeekDay(2018,11,24)
--SELECT dbo.GetWeekDay(2018,11,25)
--SELECT dbo.GetWeekDay(2018,11,26)
 --SELECT dbo.GetWeekDay(2018,11,20)
 --SELECT dbo.GetWeekDay(2018,11,21)
 --SELECT dbo.GetWeekDay(2018,11,22)
 --SELECT dbo.GetWeekDay(2018,11,23)
 --SELECT dbo.GetWeekDay(2018,11,24)
 --SELECT dbo.GetWeekDay(2018,11,25)
 --SELECT dbo.GetWeekDay(2018,11,26)
 RETURN @weekday
END