Using Recursive query in function - sql-server

Question

I have this query developed with the help of a guy here and I am not able to use this in function.
There is some sort of Syntax issue.
Here is the query
WITH CTE AS (
SELECT #STARTDATE AS STARTDATE
UNION ALL
SELECT DATEADD(D,1,STARTDATE)
FROM CTE
WHERE STARTDATE <#ENDDATE
),
WORKINGDAYS AS (
SELECT STARTDATE,
DATENAME(DW,STARTDATE)WEEKDAYS,
C1.CalanderDayName AS isweekend
FROM CTE c
LEFT JOIN HRM.tbl_Calendar C1 ON DATENAME(DW,STARTDATE) = C1.CalanderDayName
AND C1.IsOffDay = 1
)
SELECT COUNT(WEEKDAYS)as WORKINGDAYS
FROM WORKINGDAYS
WHERE isweekend IS NULL;
I want to create a function named fnGetWorkingDays
ALTER FUNCTION [dbo].[fnGetWorkingDays] (#StartDate datetime, #EndDate datetime)
RETURNS int
AS
BEGIN
DECLARE #dateFrom datetime
DECLARE #dateTo datetime
SET #dateFrom = #StartDate
SET #dateTo = #EndDate
DECLARE #WORKDAYS INT
SELECT #WORKDAYS =
;WITH CTE AS (
SELECT #STARTDATE AS STARTDATE
UNION ALL
select DATEADD(D,1,STARTDATE)
FROM CTE
WHERE STARTDATE <#ENDDATE
)
,WORKINGDAYS AS (
SELECT STARTDATE,DATENAME(DW,STARTDATE)WEEKDAYS, C1.CalanderDayName AS isweekend
FROM CTE c
LEFT JOIN HRM.tbl_Calendar C1 ON DATENAME(DW,STARTDATE)=C1.CalanderDayName AND C1.IsOffDay=1
)
SELECT COUNT(WEEKDAYS)as WORKINGDAYS FROM WORKINGDAYS WHERE isweekend is null
RETURN #WORKDAYS
END

Answer 1

Try With this Below function .let me know back for any errors
CREATE FUNCTION [dbo].[fnGetWorkingDays] (#StartDate datetime, #EndDate datetime)
RETURNS int
AS
BEGIN
DECLARE #WORKDAYS INT
;WITH CTE AS (
SELECT #STARTDATE AS STARTDATE
UNION ALL
SELECT DATEADD(D,1,STARTDATE)
FROM CTE
WHERE STARTDATE <#ENDDATE
),
WORKINGDAYS AS (
SELECT STARTDATE,
DATENAME(DW,STARTDATE)WEEKDAYS,
C1.CalanderDayName AS isweekend
FROM CTE c
LEFT JOIN HRM.tbl_Calendar C1 ON DATENAME(DW,STARTDATE) = C1.CalanderDayName
AND C1.IsOffDay = 1
)
SELECT #WORKDAYS=COUNT(WEEKDAYS) FROM WORKINGDAYS WHERE isweekend is null
RETURN #WORKDAYS
END

Answer 2

You are getting the Error because your Assignment operation for the Variable #WORKDAYS is Wrong. Change it Like This
ALTER FUNCTION [dbo].[fnGetWorkingDays]
(
#StartDate DATETIME,
#EndDate DATETIME
)
RETURNS INT
AS
BEGIN
DECLARE #dateFrom DATETIME;
DECLARE #dateTo DATETIME;
SET #dateFrom = #StartDate;
SET #dateTo = #EndDate;
DECLARE #WORKDAYS INT;
WITH CTE
AS
(
SELECT
#STARTDATE AS STARTDATE
UNION ALL
SELECT
DATEADD(D, 1, STARTDATE)
FROM CTE
WHERE STARTDATE < #ENDDATE
),WORKINGDAYS
AS
(
SELECT
DATENAME(DW, STARTDATE) WEEKDAYS,
C1.CalanderDayName AS isweekend
FROM CTE c
LEFT JOIN HRM.tbl_Calendar C1
ON DATENAME(DW, STARTDATE) = C1.CalanderDayName
AND C1.IsOffDay = 1
)
SELECT
#WORKDAYS = COUNT(WEEKDAYS)--Asign Variable Here
FROM WORKINGDAYS
WHERE isweekend IS NULL;
RETURN #WORKDAYS;
END;

Answer 3

You have written wrong syntax to set #WORKDAYS, try below syntax
CREATE FUNCTION [dbo].[fnGetWorkingDays] (#StartDate datetime, #EndDate datetime)
RETURNS int
AS
BEGIN
DECLARE #WORKDAYS INT
;WITH CTE AS (
SELECT #STARTDATE AS STARTDATE
UNION ALL
select DATEADD(D,1,STARTDATE)
FROM CTE
WHERE STARTDATE <#ENDDATE
)
,WORKINGDAYS AS (
SELECT STARTDATE,DATENAME(DW,STARTDATE)WEEKDAYS, C1.CalanderDayName AS isweekend
FROM CTE c
LEFT JOIN HRM.tbl_Calendar C1 ON DATENAME(DW,STARTDATE)=C1.CalanderDayName AND C1.IsOffDay=1
)
SELECT #WORKDAYS=COUNT(WEEKDAYS) FROM WORKINGDAYS WHERE isweekend is null
RETURN #WORKDAYS
END