add DateAddBusinessDays

Author: davidnguye

utility/DateAddBusinessDays.sql

@@ -0,0 +1,33 @@
+--======================================================
+-- Usage:	DateAddBusinessDays
+-- History:
+-- Date			Author		Description
+-- 2020-06-10	DN			Intial
+--======================================================
+DROP FUNCTION IF EXISTS DateAddBusinessDays
+GO
+CREATE FUNCTION DateAddBusinessDays
+(
+    @Days int,
+    @Date datetime  
+)
+RETURNS datetime
+AS 
+BEGIN
+	DECLARE @DayOfWeek int
+    SET @DayOfWeek = CASE 
+                        WHEN @Days < 0 THEN (@@DateFirst + DATEPART(weekday, @Date) - 20) % 7
+                        ELSE (@@DateFirst + DATEPART(weekday, @Date) - 2) % 7
+                     END;
+
+    IF @DayOfWeek = 6
+		SET @Days = @Days - 1
+    ELSE IF @DayOfWeek = -6
+		SET @Days = @Days + 1;
+
+    RETURN @Date + @Days + (@Days + @DayOfWeek) / 5 * 2;
+END
+/*
+SELECT dbo.DateAddBusinessDays(-2,GETDATE())
+SELECT dbo.DateAddBusinessDays(5,GETDATE())
+*/