Technical Article

IsWorkday UDF without a table

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While the other methods for calculating holidays ect use a table to store the holidays, this inline UDF goes the opposite route, by returning 1 if the given date is a weekday that also does not fall on a number of holidays.  Examples shown allow for easy extension to other holidays as deemed necessary.

/*****************************************************************************
* funcIsWorkday - Returns 1 if the specified date is a M-F workday that does
* not fall on any of the following holidays:
*New Years Day, Memorial Day, Independence Day, Labor Day,
*Thanksgiving Day and day after, Christmas even, Christmas
*day after Christmas, New Years Eve
******************************************************************************/CREATE FUNCTION [funcIsWorkday]
(
@dtDate datetime
)
RETURNS int AS  
BEGIN 
DECLARE @inDW int
DECLARE @inMonth int
DECLARE @inDay int
DECLARE @inYear int
DECLARE @dtTemp datetime

SET @inDW = DATEPART(dw,@dtDate)

-- Saturday or Sunday
IF (@inDW = 1 OR @inDW = 7)
RETURN 0

-- New years day
IF (@inMonth = 1 AND @inDay = 1)
RETURN 0

-- Memorial Day
IF (@inMonth = 5)
BEGIN
-- Last Monday in the month of May
SET @dtTemp = CAST(('6/1/' + CAST(@inYear AS varchar)) AS datetime)
SET @dtTemp = CASE(DATEPART(dw,@dtTemp))
WHEN 1 THEN DATEADD(dd,-6,@dtTemp)-- Sunday after
WHEN 2 THEN DATEADD(dd,-7,@dtTemp)-- Monday week after
ELSE DATEADD(dd,2-DATEPART(dw,@dtTemp),@dtTemp)
END

IF (@inDay = DAY(@dtTemp))
RETURN 0
END

-- Independence Day
IF (@inMonth = 7 AND @inDay = 4)
RETURN 0

-- Labor Day
-- First Monday in September
IF (@inMonth = 9)
BEGIN
SET @dtTemp = CAST(('9/1/' + CAST(@inYear AS varchar)) AS datetime)
SET @dtTemp = CASE(DATEPART(dw,@dtTemp))
WHEN 1 THEN DATEADD(dd,1,@dtTemp) -- Before Mondy
WHEN 2 THEN @dtTemp -- First of the month
ELSE DATEADD(dd,(7-DATEPART(dw,@dtTemp)+2),@dtTemp) -- After Monday
END

IF (@inDay = DAY(@dtTemp))
RETURN 0
END


-- Thanksgiving Day or day after
-- Fourth Thursday/Friday in November
IF (@inMonth = 11)
BEGIN
SET @dtTemp = CAST(('11/1/' + CAST(@inYear AS varchar)) AS datetime)

SET @dtTemp = CASE 
WHEN DATEPART(dw,@dtTemp) < 5 THEN
DATEADD(dd,5-DATEPART(dw,@dtTemp)+21,@dtTemp) -- Before thursday
WHEN DATEPART(dw,@dtTemp) = 5 THEN
DATEADD(dd,21,@dtTemp)-- Thursday
ELSE DATEADD(dd,7-DATEPART(dw,@dtTemp)+5+21,@dtTemp)-- After thusday
      END
IF (@inDay = DAY(@dtTemp))
RETURN 0 -- Thanksgiving

IF (@inDay - 1 = DAY(@dtTemp))
RETURN 0 -- Day after
END

-- Christmas eve, xmas, day after, new years eve
IF (@inMonth = 12 AND 
(@inDay = 24 OR @inDay = 25 OR @inDay = 26 OR @inDay = 31))
RETURN 0

-- Must be a workday
RETURN 1
END

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