SQL Server trigger's cursor is not working - sql

Question

I created a cursor inside a trigger and it is not working properly. Please help me fix it
Create trigger Posts_Raw_To_Queue_Trigger ON SendNotificationPostsRaw FOR INSERT
AS
BEGIN
DECLARE #PostID uniqueidentifier
DECLARE #UserID uniqueidentifier
DECLARE #ProfID int
DECLARE #Email nvarchar(100)
DECLARE #CreationTime datetime
DECLARE #SpecialityID int
SELECT #ProfID= ProfessionalID,#Email= Email from Professionals where UserID=#UserID
SELECT #PostID = I.PostID,#UserID = I.UserID ,#CreationTime =I.CreationTime FROM INSERTED I
DECLARE post_relation_cursor CURSOR FOR select CategoryId from PostCategoryRelations where PostId=#PostID;
OPEN post_relation_cursor;
FETCH NEXT FROM post_relation_cursor INTO #SpecialityID
WHILE ##FETCH_STATUS = 0
BEGIN
INSERT INTO SendNotificationPostsQueue (UserID,PostID,SpecialityID,TemplateID,CreationTime,SendTime,JSONParameters) Values(#UserID,#PostID,1,1,'04/11/2013','04/11/2013','')
FETCH NEXT FROM post_relation_cursor INTO #SpecialityID;
END;
CLOSE post_relation_cursor;
DEALLOCATE post_relation_cursor;
END
If I remove cursor and insert dummy values into SendNotificationPostsQueue, it works. So there is problem with my cursor... Please tell me why cursor is not working?

Answer 1

It doesn't appear that you need to use a cursor at all and would be better off not using one in almost all cases. Simply replace the body of your trigger (the part between begin and end) with a standard insert:
INSERT INTO SendNotificationPostsQueue (UserID,PostID,SpecialityID,TemplateID,CreationTime,SendTime,JSONParameters)
SELECT
i.UserID,
i.PostID,
1,
1,
'04/11/2013', -- Might want i.CreationTime or current_timestamp
'04/11/2013',
''
FROM INSERTED i
-- possibly want "LEFT JOIN Professionals p on i.UserID = p.UserID" here to grab other info
Note how I am not using the values clause of an insert which can only insert one row. I'm putting a select statement as part of the insert, thus inserting as many rows as the select returns. This means that we don't need to use a cursor, and don't need a bunch of variables to power the cursor.
One issue with your current code, as #automatic has mentioned, is that you're assuming INSERTED only holds one row. If it has more than one, then you'll throw an error when you try to assign a column to a variable.
For reasons of elegance, maintainability, and performance, I strongly urge you to abandon this cursor and run a simple insert (since that's all that your cursor is doing anyway).

Answer 2

Possible problem is here -
CREATE TRIGGER dbo.Posts_Raw_To_Queue_Trigger
ON SendNotificationPostsRaw
-- for view
INSTEAD OF INSERT
-- OR
-- for table
AFTER INSERT
AS BEGIN
DECLARE
#PostID UNIQUEIDENTIFIER
, #UserID UNIQUEIDENTIFIER
, #ProfID INT
, #Email NVARCHAR(100)
, #CreationTime DATETIME
, #SpecialityID INT
SELECT #ProfID = ProfessionalID
, #Email = Email
FROM Professionals
WHERE UserID = #UserID
-- this posible return invalid result (random record from inserted sequence)
SELECT #PostID = I.PostID
, #UserID = I.UserID
, #CreationTime = I.CreationTime
FROM INSERTED I
DECLARE post_relation_cursor CURSOR LOCAL READ_ONLY FAST_FORWARD FOR
SELECT CategoryID
FROM dbo.PostCategoryRelations
WHERE PostId = #PostID;
OPEN post_relation_cursor;
FETCH NEXT FROM post_relation_cursor INTO #SpecialityID
WHILE ##FETCH_STATUS=0 BEGIN
INSERT INTO SendNotificationPostsQueue (
UserID
, PostID
, SpecialityID
, TemplateID
, CreationTime
, SendTime
, JSONParameters
)
SELECT
#UserID
, #PostID
, #SpecialityID --- !!!
, 1
, '04/11/2013'
, '04/11/2013'
, ''
FETCH NEXT FROM post_relation_cursor INTO #SpecialityID;
END;
CLOSE post_relation_cursor;
DEALLOCATE post_relation_cursor;
END
Update
If I understand you correctly, the business logic must be like this:
CREATE TRIGGER dbo.Posts_Raw_To_Queue_Trigger
ON dbo.SendNotificationPostsRaw
[INSTEAD OF]/[AFTER] INSERT
AS BEGIN
SET NOCOUNT ON;
DECLARE
#PostID UNIQUEIDENTIFIER
, #UserID UNIQUEIDENTIFIER
, #ProfID INT
, #Email NVARCHAR(100)
, #CreationTime DATETIME
, #SpecialityID INT
DECLARE cur CURSOR LOCAL READ_ONLY FAST_FORWARD FOR
SELECT
i.PostID
, i.UserID
, ProfID = p.ProfessionalID
, p.Email
, i.CreationTime
, pcr.CategoryID
FROM INSERTED i
JOIN dbo.Professionals p ON i.UserID = p.UserID
JOIN dbo.PostCategoryRelations pcr ON i.PostID = pcr.PostID
OPEN cur
FETCH NEXT FROM cur INTO
#PostID
, #UserID
, #ProfID
, #Email
, #CreationTime
, #SpecialityID
WHILE ##FETCH_STATUS = 0 BEGIN
INSERT INTO dbo.SendNotificationPostsQueue
(
UserID
, PostID
, SpecialityID
, TemplateID
, CreationTime
, SendTime
, JSONParameters
)
SELECT
#UserID
, #PostID
, #SpecialityID
, 1
, #CreationTime
, #CreationTime
, ''
FETCH NEXT FROM cur INTO
#PostID
, #UserID
, #ProfID
, #Email
, #CreationTime
, #SpecialityID
END
CLOSE cur
DEALLOCATE cur
END