Update multiple columns by ids - sql

Question

I have tables called tblPurchase and tblInvoice. When I Insert new record I want to update my TotalStock form tblInvoice. I tried following code.
Create procedure [dbo].[spUpdateTotalStock] #Stock int, #PurchaseId int
As
Begin
Begin Transaction
Update tblPurchase
Set TotalStock = #Stock
Where PurchaseId = #PurchaseId
RollBack Transaction
end
It worked as expected. But I want to update TotalStock column by many ids. It means when I insert more than one invoice at the same time, I want to update my TotalStock column. like this
tblInvoice
ItemName | Quantity
---------+----------
Phone 3
Mouse 6
tblPurchase
ItemName | TotalStock
-----------+------------
phone 3
Mouse 6
ID comes with parameter. Always more than 10 ids come with parameter.

Answer 1

When I Insert new record I want to update my TotalStock form tblInvoice
This would normally be handled via a trigger not a stored procedure. That would look something like this:
create trigger trig_invoice_update on tblInvoice
after insert, update, delete
begin
update p
set quantity = p.quantity + coalesce(i.quantity, 0) - coalesce(d.quantity, 0)
from tblPurchase p left join
(select i.itemName, sum(i.quantity) as quantity
from inserted i
group by i.itemName
) i
on p.itemName = i.itemName left join
(select d.itemName, sum(d.quantity) as quantity
from deleted d
group by d.itemName
) d
on p.itemName = d.itemName
where d.quantity <> 0 or i.quantity <> 0;
end;
This version handles inserts, updates, and deletes, but assumes that all items are already in the purchases table.