SQL Server Trigger Error Message - sql-server

Question

This is the error I am getting:
Msg 512, Level 16, State 1, Procedure tr_UpdateFolio, Line 361
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
I've run up and down this code over and over for hours now. What am I not seeing? Any help would be appreciated. I've been working on this for a few days now, and this is pretty much the one thing I need working in order to get this project done.
-- 2. Write a trigger named tr_UpdateFolio that will be invoked when the Folio table 'status'
-- field ONLY (column update) is changed.
ALTER TRIGGER tr_UpdateFolio ON FOLIO--switch alter back to create
AFTER UPDATE
AS
IF UPDATE([Status])
BEGIN
DECLARE #Status char(1)
DECLARE #FolioID smallint
DECLARE #CheckinDate smalldatetime
DECLARE #Nights tinyint
DECLARE #CurrentDate smalldatetime = '7/27/2016 2:00:00 PM'
SELECT
#Status = i.Status,
#FolioID = i.FolioID,
#CheckinDate = i.CheckinDate,
#Nights = i.Nights
FROM
INSERTED i
-- If Folio status is updated to 'C' for Checkout, trigger two different Insert statements to
-- (1) INSERT in the Billing table, the amount for the total lodging cost as BillingCategoryID1
-- - (normally the FolioRate * number of nights stay, but you must also factor in any late checkout fees*).
-- *Checkout time is Noon on the checkout date. Guest is given a one hour
-- grace period to check out. After 1PM (but before 4PM), a 50% surcharge is added to the FolioRate. After 4PM, an
-- additional full night's FolioRate is applied. You can recycle code from A7 (part 5), but note it's not the exact same
-- function - we only need the late charge (if any).
IF #Status = 'C'
SET #Nights = 1
--#CurrentDate may need to switch back to getdate()
IF DATEDIFF(HOUR, #CheckinDate + #Nights, #CurrentDate) >= 16
SET #Nights = #Nights + 1
ELSE IF DATEDIFF(HOUR, #CheckinDate + #Nights, #CurrentDate) >= 13
SET #Nights = #Nights + .5
UPDATE FOLIO
SET Nights = #Nights
WHERE FolioID = #FolioID
INSERT INTO BILLING (FolioID, BillingCategoryID, BillingDescription, BillingAmount, BillingItemQty, BillingItemDate)
VALUES (25, 1, 'Room', dbo.GetRackRate(11, #CurrentDate) * #Nights, 1, #CurrentDate)
-- (2) The second INSERT statement in the same trigger will insert the Lodging Tax* - as a separate entry in the
-- Billing table for tax on lodging (BillingCategoryID2). *Use the dbo.GetRoomTaxRate function from A7 to determine
-- the Lodging Tax.
INSERT INTO BILLING (FolioID, BillingCategoryID, BillingDescription, BillingAmount, BillingItemQty, BillingItemDate)
VALUES (25, 2, 'Lodging Tax', dbo.GetRoomTaxRate(20), 1, #CurrentDate)
END
GO
-- 3. Write a trigger named tr_GenerateBill that will be invoked when an entry is INSERTED in to the Billing
-- table. If BillngCategoryID is 2 (for testing purposes only) then call the function dbo.ProduceBill (from A7).
ALTER TRIGGER tr_GenerateBill ON BILLING
AFTER INSERT
AS
BEGIN
DECLARE #FolioID smallint
DECLARE #BillingCategoryID smallint
SELECT #FolioID = i.FolioID, #BillingCategoryID = i.BillingCategoryID
FROM INSERTED i
IF #BillingCategoryID = 2
SELECT * FROM dbo.ProduceBill(#FolioID)
END
GO
dbo.producebill should be fine, but the error occurs when I try to run this block
-- 4A. Assume today is (July 27, 2016 at 2PM)*. Anita is due to check out today (from Part 1 above).
-- Write an Update Statement to change the status of her Folio to 'CheckedOut.
-- (Be careful to include a WHERE clause so ONLY here folio is updated).
-- Note: This should automatically invoke tr_UpdateFolio above (factoring in the late charge),
-- which automatically invokes tr_GenerateBill above, and calls dbo.ProduceBill , and produces a bill.
UPDATE FOLIO
SET [Status] = 'C'
WHERE ReservationID = 5020
I'm going nuts trying to figure this out. Thanks.

Answer 1

Let's start with the easier one (tr_GenerateBill). This one is a little odd for sure. You have a select statement in an insert trigger. This means that when you insert a row you are expecting it to return row(s). This is not the typical behavior of an insert but you can work with it.
If you insert 3 rows and only 2 of them have a BillingCategoryID of 2 what should the trigger do? What does that table valued function look like?
This is kind of a guess but you should be able to rewrite that entire trigger to something along these lines.
ALTER TRIGGER tr_GenerateBill ON BILLING
AFTER INSERT
AS
BEGIN
SELECT *
FROM inserted i
cross apply dbo.ProduceBill(i.FolioID) pb
where i.BillingCategoryID = 2
END
Your second trigger is more challenging. It is not totally clear what you are trying to do here but I think this is pretty close.
UPDATE f
set Nights = case when DATEDIFF(HOUR, #CheckinDate + i.Nights, #CurrentDate) >= 16 then 2 else 1 end --adding .5 to a tiny int is pointless. It will ALWAYS be the same value.
from inserted i
join Folio f on f.FolioID = i.FolioID
INSERT INTO BILLING (FolioID, BillingCategoryID, BillingDescription, BillingAmount, BillingItemQty, BillingItemDate)
Select i.FolioID
, 1
, 'Room'
, dbo.GetRackRate(11, #CurrentDate) * case when DATEDIFF(HOUR, #CheckinDate + i.Nights, #CurrentDate) >= 16 then 2 else 1 end, 1, #CurrentDate)
from inserted i
INSERT INTO BILLING (FolioID, BillingCategoryID, BillingDescription, BillingAmount, BillingItemQty, BillingItemDate)
select i.FolioID
, 2
, 'Lodging Tax'
, dbo.GetRoomTaxRate(20), 1, #CurrentDate)
from inserted i