Failure creating a function same as stored procedure - sql-server

Question

This is my stored procedure which I was able to create
CREATE PROCEDURE [dbo].[spGetAllStaffCollectiveAttendanceByMonth]
#Month nvarchar(9)
AS
BEGIN
Declare #StartDate DATE,
#EndDate DATE
;WITH CteMonths(n, m) AS(
SELECT 1, 'January' UNION ALL
SELECT 2, 'February' UNION ALL
SELECT 3, 'March' UNION ALL
SELECT 4, 'April' UNION ALL
SELECT 5, 'May' UNION ALL
SELECT 6, 'June' UNION ALL
SELECT 7, 'July' UNION ALL
SELECT 8, 'August' UNION ALL
SELECT 9, 'September' UNION ALL
SELECT 10, 'October' UNION ALL
SELECT 11, 'November' UNION ALL
SELECT 12, 'December'
)
SELECT #StartDate = DATEADD(MONTH, n - 1, DATEADD(YEAR, DATEDIFF(YEAR, 0, GETDATE()), 0)),
#EndDate = DATEADD(DAY, -1, DATEADD(MONTH, n, DATEADD(YEAR, DATEDIFF(YEAR, 0, GETDATE()), 0)))
FROM CteMonths
WHERE m = #month
SELECT
StaffAttendance.StaffId,
DATENAME(MONTH, #StartDate) AS [ForMonth], #StartDate AS StartDate, #EndDate AS EndDate,
(DATEDIFF(dd, #StartDate, #EndDate) + 1)-(DATEDIFF(wk, #StartDate, #EndDate) * 1)-(CASE WHEN DATENAME(dw, #StartDate) = 'Sunday' THEN 1 ELSE 0 END) AS TotalWorkingDays,
SUM(StaffAttendance.AttendanceStatusId) AS TotalDaysWorked
FROM StaffAttendance
WHERE [Date] BETWEEN #StartDate AND #EndDate AND StaffAttendance.AttendanceStatusId = 1 GROUP BY StaffAttendance.StaffId
END
GO
This, here, is my function which I am trying to create but can't. Its the same thing as above except for what makes it a function.
CREATE FUNCTION [dbo].[funcGetAllStaffCollectiveAttendanceByMonth]
(
#Month nvarchar(9)
)
RETURNS TABLE
AS
RETURN
(
Declare #StartDate DATE,
#EndDate DATE
;WITH CteMonths(n, m) AS(
SELECT 1, 'January' UNION ALL
SELECT 2, 'February' UNION ALL
SELECT 3, 'March' UNION ALL
SELECT 4, 'April' UNION ALL
SELECT 5, 'May' UNION ALL
SELECT 6, 'June' UNION ALL
SELECT 7, 'July' UNION ALL
SELECT 8, 'August' UNION ALL
SELECT 9, 'September' UNION ALL
SELECT 10, 'October' UNION ALL
SELECT 11, 'November' UNION ALL
SELECT 12, 'December'
)
SELECT #StartDate = DATEADD(MONTH, n - 1, DATEADD(YEAR, DATEDIFF(YEAR, 0, GETDATE()), 0)),
#EndDate = DATEADD(DAY, -1, DATEADD(MONTH, n, DATEADD(YEAR, DATEDIFF(YEAR, 0, GETDATE()), 0)))
FROM CteMonths
WHERE m = #month
SELECT
StaffAttendance.StaffId,
DATENAME(MONTH, #StartDate) AS [ForMonth], #StartDate AS StartDate, #EndDate AS EndDate,
(DATEDIFF(dd, #StartDate, #EndDate) + 1)-(DATEDIFF(wk, #StartDate, #EndDate) * 1)-(CASE WHEN DATENAME(dw, #StartDate) = 'Sunday' THEN 1 ELSE 0 END) AS TotalWorkingDays,
SUM(StaffAttendance.AttendanceStatusId) AS TotalDaysWorked
FROM StaffAttendance
WHERE [Date] BETWEEN #StartDate AND #EndDate AND StaffAttendance.AttendanceStatusId = 1 GROUP BY StaffAttendance.StaffId
END
)
But this is what I am getting
What am I doing wrong?

Answer 1

You have used the syntax for an inline table-valued function but you have multiple statements.
Comparison of inline and multi-statement table-valued functions.
So you could either refactor to use a single statement (higher performance) or use the multi-statement syntax as described in that link (easier).
If you wanted to do it inline you could do something along these lines (note, I don't have SSMS available right now so there may be some minor syntax errors like unmatched brackets):
CREATE FUNCTION [dbo].[funcGetAllStaffCollectiveAttendanceByMonth]
(
#Month nvarchar(9)
)
RETURNS TABLE
AS
RETURN
(
-- The StartDate should be the first day of the month that is passed as a parameter, in the current year.
-- The EndDate should be the last day of the month which the StartDate begins.
WITH cteDates AS (
SELECT StartDate = Convert(date, Concat('01', #Month, Convert(varchar(4), DatePart(Year, GetDate()))), 106),
EndDate = DateAdd(Day, -1,
DateAdd(Month, 1,
Convert(date, Concat('01', #Month, Convert(varchar(4), DatePart(Year, GetDate()))) , 106)
)
)
)
SELECT
Sa.StaffId,
DATENAME(MONTH, cteDates.StartDate) AS [ForMonth],
cteDates.StartDate,
cteDates.EndDate,
(DATEDIFF(dd, cteDates.StartDate, cteDates.EndDate) + 1)-
(DATEDIFF(wk, cteDates.StartDate, cteDates.EndDate) * 1)-
(CASE WHEN DATENAME(dw, cteDates.StartDate) = 'Sunday' THEN 1 ELSE 0 END) AS TotalWorkingDays,
SUM(sa.AttendanceStatusId) AS TotalDaysWorked
FROM StaffAttendance As sa
JOIN cteDates ON sa.[Date] BETWEEN cteDates.StartDate AND cteDates.EndDate
WHERE sa.AttendanceStatusId = 1
GROUP BY
Sa.StaffId,
DATENAME(MONTH, cteDates.StartDate),
cteDates.StartDate,
cteDates.EndDate,
(DATEDIFF(dd, cteDates.StartDate, cteDates.EndDate) + 1)-
(DATEDIFF(wk, cteDates.StartDate, cteDates.EndDate) * 1)-
(CASE WHEN DATENAME(dw, cteDates.StartDate) = 'Sunday' THEN 1 ELSE 0 END)
END
)