[mssql] Get First Date of Previous Month

CREATE FUNCTION dbo.udf_FirstDayofPreviousMonth (@pDate datetime)
RETURNS datetime
AS
BEGIN
 DECLARE @dFirstDayPrefMonth AS datetime

 SET @dFirstDayPrefMonth =
       convert(datetime,
                  left(convert(varchar(8),
                  dateadd(MM,-1, @pDate), 112), 6) + '01', 112)

 RETURN @dFirstDayPrefMonth
END
GO