SQL Trigger doesn't execute triggers procedure - sql-server

Question

In SQL management studio I want to add trigger to one table. When data is inserted into table I want to insert or update data in other tables if some requirements are met.
ALTER trigger [dbo].[game_data_received]
on [dbo].[GameRounds]
for insert
as
declare #LastDate datetime
declare #CurrDate datetime
declare #GameID int
declare #TimeDiff int
declare #CurrMult int
declare #MaxMult int
declare #MaxDiff int
select #GameID = i.GameID from inserted i
select #CurrDate = i.[TimeStamp] from inserted i
select #CurrMult = i.MaxMultiplier from inserted i
select #LastDate = max([TimeStamp]) from GameRounds where GameID = #GameID
select #TimeDiff = DATEDIFF(SECOND, #LastDate, #CurrDate)
select #MaxDiff = (select TimeDifference from AcceptableTimeDiffGameRounds where GameID = #GameID)
select #MaxMult = (select MaxMultiplier from AcceptableTimeDiffGameRounds where GameID = #GameID)
if #TimeDiff > #MaxDiff
if #CurrMult >= #MaxMult
update AcceptableTimeDiffGameRounds
set MaxMultiplier = #CurrMult, TimeDifference = #TimeDiff
where GameID = #GameID
else
insert into Defects(DownFrom, DownUntill)
values (#LastDate, #CurrDate)
So this is my trigger query. Data in the GameRounds table are inserted automaticaly, but it doesn't executes this whole procedure. I can tell this because, when I select the tables where data should be added or change they stay same. Thanks in advance.

Answer 1

SQL Server is a SET-based language and the best practice is to handle it as such.
A commom misconception with triggers is that they're only responsible for 1 row, however, an insert trigger could have 1 or thousands of rows. The trigger you shared only handles a single inserted record (last in)--not all of them.
While I would not recommend handling your request this way--it really should be written to handle the entire inserted rowset at once--I have had to process an insert row-by-agonizing-row (RBAR) in the past. In this case, you could try rewriting your trigger like the following:
DECLARE #GameID int, #CurrDate datetime, #CurrMult int, #row_id int = 1;
DECLARE #inserted_rows table (
GameID int, CurrDate datetime, CurrMult int, row_id int IDENTITY ( 1, 1 )
);
INSERT INTO #inserted_rows (
GameID, CurrDate, CurrMult
)
SELECT
GameID, [TimeStamp], MaxMultiplier
FROM inserted;
WHILE #row_id <= ( SELECT MAX ( row_id ) FROM #inserted_rows )
BEGIN
-- Current row.
SELECT
#GameID = GameID, #CurrDate = CurrDate, #CurrMult = CurrMult
FROM #inserted_rows WHERE row_id = #row_id;
-- Process row.
DECLARE #MaxMult int, #MaxDiff int;
DECLARE #LastDate datetime = ( SELECT MAX( [TimeStamp] ) FROM GameRounds WHERE GameID = #GameID );
DECLARE #TimeDiff int = DATEDIFF( second, #LastDate, #CurrDate);
SELECT
#MaxMult = MaxMultiplier,
#MaxDiff = TimeDifference
FROM AcceptableTimeDiffGameRounds
WHERE
GameID = #GameID;
IF #TimeDiff > #MaxDiff
BEGIN
IF #CurrMult >= #MaxMult
UPDATE AcceptableTimeDiffGameRounds
SET
MaxMultiplier = #CurrMult,
TimeDifference = #TimeDiff
WHERE GameID = #GameID;
END
ELSE
BEGIN
INSERT INTO Defects ( DownFrom, DownUntill )
VALUES ( #LastDate, #CurrDate );
END
-- Next row.
SET #row_id = #row_id + 1;
END
This example captures all of the inserted rows and then processes them one at a time (without using a cursor)--which can be painfully slow, not to mention locking issues.
Ideally, you would rewrite this using a set-based approach.