Trigger reverses the changes made - SQL Server - sql-server

Question

I'm working on an E-commerce system where I have an order table that stores all the information regarding an order. The orders go through different stages: Open, Verified, In Process, etc. And I'm keeping counts of these orders at different stages e.g. Open Orders 95, Verified 5, In Process 3, etc.
When a new order is inserted in the table, I have a trigger that increments the Open Orders by 1. Similarly, I have a trigger for updates which checks the order's previous stage and the next to decrement and increment accordingly.
The INSERT trigger is working fine as described above. But the UPDATE trigger has a weird behavior that it makes the desired changes to the Counts but then reverses the changes for some reason.
For instance, upon changing the status of an order from Open to Verified, the ideal behavior would be to decrement Open Orders by 1 and increment Verified Orders by 1. The trigger currently performed the desired action but then for some reason restores the previous value.
Here's a snippet of my trigger where I check if the order previously belonged to the Open status and is now being updated to Verified status:
IF ##ROWCOUNT = 0 RETURN
DECLARE #orderID VARCHAR(MAX) -- orderID of the order that is being updated
DECLARE #storeID VARCHAR(MAX) -- storeID of the store the order belongs to
SELECT TOP 1
#orderID = i.id,
#storeID = i.storeID
FROM
inserted AS i
INNER JOIN deleted AS d
ON i.id = d.id
-- IF from Open Order
IF EXISTS (
SELECT *
FROM
deleted
WHERE
orderStatus = 'Open' AND
id = #orderID
)
BEGIN
-- IF to Verified Order
IF EXISTS (
SELECT *
FROM
inserted
WHERE
orderStatus = 'Verified' AND
id = #orderID
)
BEGIN
UPDATE order_counts
SET
open_orders = open_orders - ##ROWCOUNT,
verified_orders = verified_orders + ##ROWCOUNT
WHERE storeID = #storeID
END
END
EDIT:
Here's some extra information which will be helpful in light of the first comment on the question:
I have a lot of records in the table so using COUNT() again and again has a lot of impact on the overall performance. This is why I'm keeping counts in a separate table. Also, I've written the trigger in a way that it handles both single record/multi record changes. I only check one row because I know in case of multiple records they will all be going through the same change of status. Hence, the decrement/increment of ##ROWCOUNT

Answer 1

If you can tolerate a slightly different representation of the order counts, I'd strongly suggest using an indexed view instead1:
create table dbo.Orders (
ID int not null,
OrderStatus varchar(20) not null,
constraint PK_Orders PRIMARY KEY (ID)
)
go
create view dbo.OrderCounts
with schemabinding
as
select
OrderStatus,
COUNT_BIG(*) as Cnt
from
dbo.Orders
group by OrderStatus
go
create unique clustered index IX_OrderCounts on dbo.OrderCounts (OrderStatus)
go
insert into dbo.Orders (ID,OrderStatus) values
(1,'Open'),
(2,'Open'),
(3,'Verified')
go
update dbo.Orders set OrderStatus = 'Verified' where ID = 2
go
select * from dbo.OrderCounts
Results:
OrderStatus Cnt
-------------------- --------------------
Open 1
Verified 2
This has the advantage that, whilst behind the scenes SQL Server is doing something very similar to running triggers, this code has been debugged thoroughly and is correct.
In your current attempted trigger, one further reason why the trigger is currently broken is that ##ROWCOUNT isn't "sticky" - it doesn't remember the number of rows that were affected by the original UPDATE when you're running other statements inside your trigger that also set ##ROWCOUNT.
1You can always stack a non-indexed view atop this view and perform a PIVOT if you really want the counts in a single row and in multiple columns.

Answer 2

The reason for this behavior is the use of ##ROWCOUNT multiple times while in reality once the results from ##ROWCOUNT is fetched, the results are cleared. Instead get the results into variable and use that variable across the trigger. Check the below scenario for the same.
CREATE DATABASE Test
USE Test
CREATE TABLE One
(
ID INT IDENTITY(1,1)
,Name NVARCHAR(MAX)
)
GO
CREATE TRIGGER TR_One ON One FOR INSERT,UPDATE
AS
BEGIN
PRINT ##ROWCOUNT
SELECT ##ROWCOUNT
END
UPDATE One
SET Name = 'Name4'
WHERE ID = 3
RESULTS :-
The Print ##ROWCOUNT statement would give a value of 1, where as the select ##ROWCOUNT would give the value of 0