SELECT DATEFROMPARTS(Year(Getdate()),Month(getdate()),1) AS FirstDayofMonth
select DATEADD(day,1,Eomonth(getdate(),-1)) AS FirstDayofMonth
Select CONVERT(date,Format(getdate(),'yyyy-MM-01')) AS FirstDayofMonth
select Dateadd(day,1-day(Getdate()),getdate()) AS FirstDayofMonth