Trigger to update value with no of records - sql

Question

trying to set up a trigger but struggling to it to work the way i want, i want to update a field oppo_pono with the no of opportunity records created for a particular company record
so 1 company can have multiple opportunities and i want to record the no of master opportunities created for a company, so the first master opp created for a company would be set to 1 and so on
ive set the trigger up below but its setting the oppo_pono with the count from all companies rather then the one i am creating the opportunity for
my trigger below
USE [CRM]
GO
/****** Object: Trigger [dbo].[GeneratePNo] Script Date: 1/7/2021 3:55:27 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER TRIGGER [dbo].[GeneratePNo]
ON [dbo].[Opportunity]
FOR insert
AS
declare #OppPrimary Int
declare #company Int
declare #compid Int
declare #type nvarchar(40)
declare #childopp nchar(1)
declare #pono int
Select #OppPrimary = Oppo_OpportunityId,
#company = Oppo_PrimaryCompanyId,
#compid = comp_companyid,
#type = Oppo_Type,
#childopp = oppo_childoppo,
#pono = oppo_pono
FROM Inserted inner join company on Oppo_PrimaryCompanyId = #compid
Begin
UPDATE [Opportunity] SET oppo_pono = (select count(*) from vSearchListOpportunity where Oppo_Deleted is null and #type = 'Master' and Oppo_PrimaryCompanyId = ) +1
WHERE Oppo_OpportunityId =#OppPrimary
End

Answer 1

As mentioned in the comments, you have not taken into account the inserted pseudo-table having multiple rows. You also have a number of outright syntax errors.
EDIT: Following your comments I think I understand what you are trying to do. My original solution will not work here because indexed view cannot have ranking functions, but I have modified it to work with what you need.
Ideally, you wouldn't care about the actual IDs lining up, and just use an IDENTITY column, but often an ID series per group is needed.
Generally a view with correct indexing will be the more performant option, but it depends what you need.
Using a View
I will show you a solution that can be used for a lot of different types of aggregations which normally require triggers. This only works for your problem if you intend to have the numbering change if a row gets deleted out the middle of the grouping. If you want the numbering to remain then use a trigger instead
I am unsure the exact relation of Opportunity, Company and vSearchListOpportunity (seems to be a view on Opportunity) but you should be able to modify this to suit.
Create an indexed view on the data, and include a row number for each row:
CREATE VIEW vOpportunityNumbered
AS
SELECT
o.Oppo_OpportunityId,
o.Oppo_PrimaryCompanyId,
o.Oppo_Type,
o.oppo_childoppo,
ROW_NUMBER() OVER
(PARTITION BY o.Oppo_PrimaryCompanyId ORDER BY o.Oppo_OpportunityId)
-- Order by primary key to get deterministic ordering
FROM Opportunity AS o
WHERE o.Oppo_Deleted IS NULL;
GO
Now, to support this view, we cannot index it directly, as mentioned. We can, however, create an index on the base table that will support it:
CREATE UNIQUE CLUSTERED INDEX opp_CompanyOpportunity
ON Opportunity (Oppo_PrimaryCompanyId, Oppo_OpportunityId)
-- note the ordering of the columns
INCLUDE (Oppo_Type, oppo_childoppo)
WITH (OPTIMIZE_FOR_SEQUENTIAL_KEY = ON) -- ONLY FOR SQL2019
;
GO
This view will now give you a sequential row numbering of Opportunity for each distinct Company.
Triggers
If you wish for the IDs to always remain the same no matter what happens to intervening rows, you will need a trigger (i.e. a deleted row will leave a gap in the numbers).
Every trigger has two tables, inserted and deleted, which contain the data that was changed. For update triggers, both tables have data, a row in each for each changed row.
This means that the trigger is executed once per statement, and these tables contain all the relevant rows. You cannot, however, update them directly; you must join the real tables to them.
So let's take a look at how to write a trigger. Again, I'm somewhat guessing as to the relations of the tables:
CREATE OR ALTER TRIGGER [dbo].[GeneratePNo]
ON [dbo].[Opportunity]
AFTER INSERT -- FOR is an alternative syntax, AFTER is more usual
AS
-- No need for BEGIN and END, the whole batch until GO is the trigger
SET NOCOUNT ON; -- Prevent DONE_IN_PROC rowcount messages
IF (NOT EXISTS (SELECT 1 FROM inserted))
RETURN; -- Bail-out early if no rows
-- We do not declare variables because we cannot store multiple rows in variables
UPDATE
o
SET oppo_pono =
ISNULL( --If there are no other rows we would get a null
(SELECT MAX(allO.oppo_pono)
FROM Opportunity allO
-- no need for the following two filters as the oppo_pono needs to be unique anyway
-- where allO.Oppo_Deleted is null and allO.type = 'Master'
WHERE allO.Oppo_PrimaryCompanyId = inserted.Oppo_PrimaryCompanyId
), 0) + 1
FROM inserted i
JOIN Opportunity o ON o.Oppo_OpportunityId = i.Oppo_OpportunityId;
-- We join inserted table on primary key always
GO
There are more efficient ways to write that update, but it depends whether you are inserting a lot of rows. An INSTEAD OF trigger will also be more performant here, but I haven't attempted that as I don't have your table definition.