How to get a inserted id in other table from inside a trigger? - sql

Question

I have 3 tables tbl_Users, tbl_Protocol and tbl_ProtocolDetails and inside of my trigger on Users, I have to inserted into Protocol and then insert into ProtocolDetails, but I don't know how work the inserted scope.
Something like that:
CREATE TRIGGER tg_Users ON tbl_Users
AFTER INSERT, UPDATE AS
BEGIN
DECLARE #UserId = Int
DECLARE #ProtocolId = Int
DECLARE #UserDetail = NVARCHAR(255)
SELECT
#UserId = user_id,
#UserDetail = user_detail + '#' + user_explanation
FROM INSERTED
INSERT INTO tbl_Protocol (user_id, inserted_date)
VALUES (#UserId, GetDate())
-- Return Inserted Id from tbl_Protocol into #ProtocolDetail then
INSERT INTO tbl_ProtocolDetails (protocol_id, protocol_details)
VALUES (#ProtocolId, #UserDetail)
END

Answer 1

Your trigger has a MAJOR flaw in that you seems to expect to always have just a single row in the Inserted table - that is not the case, since the trigger will be called once per statement (not once for each row), so if you insert 20 rows at once, the trigger is called only once, and the Inserted pseudo table contains 20 rows.
Therefore, code like this:
Select #UserId = user_id,
#UserDetail = user_detail + '#' + user_explanation
From INSERTED;
will fail, since you'll retrieve only one (arbitrary) row from the Inserted table, and you'll ignore all other rows that might be in Inserted.
You need to take that into account when programming your trigger! You have to do this in a proper, set-based fashion - not row-by-agonizing-row stlye!
Try this code:
CREATE TRIGGER tg_Users ON tbl_Users
AFTER INSERT, UPDATE AS
BEGIN
-- declare an internal table variable to hold the inserted "ProtocolId" values
DECLARE #IdTable TABLE (UserId INT, ProtocolId INT);
-- insert into the "tbl_Protocol" table from the "Inserted" pseudo table
-- keep track of the inserted new ID values in the #IdTable
INSERT INTO tbl_Protocol (user_id, inserted_date)
OUTPUT Inserted.user_id, Inserted.ProtocolId INTO #IdTable(UserId, ProtocolId)
SELECT user_id, SYSDATETIME()
FROM Inserted;
-- insert into the "tbl_ProtocolDetails" table from both the #IdTable,
-- as well as the "Inserted" pseudo table, to get all the necessary values
INSERT INTO tbl_ProtocolDetails (protocol_id, protocol_details)
SELECT
t.ProtocolId,
i.user_detail + '#' + i.user_explanation
FROM
#IdTable t
INNER JOIN
Inserted i ON i.user_id = t.UserId
END

Answer 2

There is nothing in this trigger that would handle a multiple insert/update statement. You will need to either use one scenario that will handle multiple records or check how many records were effected with a IF ##ROWCOUNT = 1 else statement. In your example, I would just use something like
insert into tbl_Protocol(user_id, inserted_date)
select user_id, user_detail + '#' + user_explanation
From INSERTED;
As for your detail table, I see Marc corrected his answer to include the multiple lines and has a simple solution or you can create a second trigger on the tbl_Protocol. Another solution I have used in the past is a temp table for processing when I have very complicated triggers.