Handling multiple rows in SQL Server trigger

Question

We have a database with a table called WarehouseItem where product\'s stock levels are kept. I need to know when ever this table get\'s updated, so I create

Answer 1

You could use a loop to iterate over INSERTED but it may be better to change your scalar variables into a TABLE and INSERT-SELECT from INSERTED where the IDs meet the criteria of the first two IFs

DECLARE @inserted TABLE (StockItemID INT, WarehouseID INT)

INSERT INTO @inserted (StockItemID, WarehouseID)
SELECT StockItemID, WarehouseID
FROM INSERTED i
WHERE dbo.IC_CanSyncProduct(i.StockItemID)=1
AND dbo.IC_CanSyncStock(i.WarehouseID)=1

then you can remove the if else upsert logic and use queries that further filter @inserted for the various updates and inserts that are required

;WITH ResetQueueEntry
(
    SELECT StockItemID
    FROM @inserted i
    WHERE EXISTS(SELECT 1 FROM IC_ProductCreateQueue q WHERE q.StockItemID = i.StockItemID)
    AND EXISTS(SELECT 1 FROM IC_StockUpdateQueue q WHERE q.StockItemID = i.StockItemID))
)

-- Reset [StockUpdate] Queue Entry
UPDATE IC_StockUpdateQueue 
SET Synced = 0
WHERE StockItemID IN (SELECT StockItemID FROM ResetStockUpdate);

WITH InsertQueueEntry
(
     SELECT StockItemId, 0 Synced
     FROM @inserted
     WHERE EXISTS(SELECT 1 FROM IC_ProductCreateQueue q WHERE q.StockItemID = i.StockItemID)       
     AND NOT EXISTS(SELECT 1 FROM IC_StockUpdateQueue q WHERE q.StockItemID = i.StockItemID))
)
-- Insert [StockUpdate] Queue Entry
INSERT INTO IC_StockUpdateQueue (StockItemID, Synced)
SELECT StockItemID, Synced
FROM InsertQueueEntry

WITH CreateProductEntry
(
     SELECT StockItemId, 0 Synced
     FROM @inserted
     WHERE NOT EXISTS(SELECT 1 FROM IC_ProductCreateQueue q WHERE q.StockItemID = i.StockItemID)
)
-- Insert [ProductCreate] Queue Entry
INSERT INTO IC_ProductCreateQueue (StockItemID, Synced)
SELECT StockItemId, Synced
FROM CreateProductEntry

WITH CreateStockEntry
(
     SELECT StockItemId, 0 Synced
     FROM @inserted
     WHERE NOT EXISTS(SELECT 1 FROM IC_ProductCreateQueue q WHERE q.StockItemID = i.StockItemID)
)
-- Insert [StockUpdate] Queue Entry
INSERT INTO IC_StockUpdateQueue (StockItemID, Synced)
SELECT StockItemId, Synced
FROM CreateProductEntry

Answer 2

in case of the trigger is for INSERT, UPDATE this code will exit the trigger IF Records are being updated AND more than one record is being afftected:

IF (SELECT COUNT(*) FROM Deleted) > 1
  BEGIN
     Return
  END

But if you wish to examin every record in the INSERTED recordset you can use this method:

   DECLARE rstAST CURSOR FOR
   SELECT ins.TaskActionId,
          _Task.CustomerId,
          _AST.ASTQRId,
          ins.ExistingQRcode,
          ins.NewQRcode
          FROM Inserted ins INNER JOIN
               dbo.cdn_AST _AST ON ins.ASTId = _AST.ASTId INNER JOIN
               dbo.tsk_Task _Task ON ins.TaskId = _Task.TaskId

    OPEN rstAST
    FETCH NEXT FROM rstAST INTO @TaskActionId, @TaskCustomerId, @ASTQRId, @ExistingQRcode, @NewQRcode
    WHILE @@FETCH_STATUS = 0
    BEGIN
      --use CONTINUE to skip next record or let it traverse the loop

      FETCH NEXT FROM rstAST INTO @TaskActionId, @TaskCustomerId, @ASTQRId, @ExistingQRcode, @NewQRcode
    END
    CLOSE rstAST
    DEALLOCATE rstAST

Answer 3

You use this:

-- Get Product Id
DECLARE @StockItemID INT = (SELECT ItemID FROM INSERTED);
DECLARE @WarehouseID INT = (SELECT WarehouseID FROM INSERTED);

But if you update multi rows (as your sample) you must use a different strategy.

For example, instead to declare a variable, use INSERTED table in JOIN in query where now you use your variable.

IF statement works on your variable but I think to move that condition in query.

Try to change you UPDATE query in this way (eventually add condition of IF):

-- Reset [StockUpdate] Queue Entry
UPDATE IC_StockUpdateQueue SET Synced = 0
FROM inserted 
WHERE inserted.itemID = StockItemID;

And so on.

For further information please add comment.