In SQL server, when does a trigger get fired?
The problem is, I have a table where 45,000 records are going to be inserted.
And I want to copy all 45k records to other tables.
But I don't want the trigger to run on every insert, i.e 45000 times trigger.
My trigger is basically copying record from TableA to TableB.
Trigger:
Create trigger tri_1
on TableA
after insert
as
Begin
Insert into TableB (ID,Name,Others)
select ID,Name,Others from TableA
inner join inserted
on inserted.ID = TableA.ID
End
The above is just the template of my trigger.
Also, I have a question, the trigger mentioned above, how is it working? like firing for each row or after all insert is done?
In SQL Server, the trigger is fired when the insert statement is completed.
In some databases, the trigger is executed for each row inserted (in those databases for each row is often part of the syntax). By contrast, SQL Server keeps track of the changed rows, which is why they are stored in table-like structures, inserted and deleted -- and it is a mistake to assume that these contain only one row.
Related
We are using an ERP system which uses SQL Server. There is a function which creates a row 'A' in a specific table and populates it with data from another row 'B' of another table. For some reason the programmer thought, one would need only certain values of 'B' in 'A'. So only the values of some columns in 'B' are copied.
Now I want more columns to be copied than the program copies. The columns are there but they don't get copied.
The program offers a way to run a script before the SQL statement, which creates the row, is executed. So the problem here is, I don't know the id of the row which will be created. And even if I would, the row isn't created yet to alter it.
Is there a way in SQL Server to run a SQL script every time after a row is created in a specific table?
Thanks for the help.
Yes - those are called triggers.
You can write triggers that get fired after INSERT, UPDATE or DELETE - or they can be INSTEAD OF triggers, too - if you need to completely take control of an operation.
In your case, I believe an AFTER INSERT trigger should be just fine:
CREATE TRIGGER TrgCopyAdditionalColumns
ON dbo.TableA
AFTER INSERT
AS
-- the newly inserted row (there could be **multiple!**)
-- will be stored in the `Inserted` pseudo table, which has the
-- exact same structure as your "TableB" table - just pick out
-- the columns you need to insert into "TableA" from here
INSERT INTO dbo.TableA (Col1, Col2, ..., ColN)
SELECT
b.Col1, b.Col2, ..., b.ColN
FROM
dbo.TableB AS b
INNER JOIN
-- somehow, you need to connect your Table B's rows to the
-- newly inserted rows for Table A that are present in the
-- "Inserted" pseudo table, to get only those rows of data from
-- Table B that are relevant to the newly inserted Table A rows
Inserted i ON b.A_ID = i.ID
Need a trigger which runs on deletion.
The code I wrote is not working: It is firing the trigger but is not inserting any records.
I want it to insert the to be deleted row in a audit table.
My code:
CREATE TRIGGER [EXERCISE].[delete_trigger] ON [EXERCISE].[Fact_Sales]
AFTER DELETE
AS
INSERT INTO [EXERCISE].[Fact_Sales_Audit](City_ID,Product_ID,Time_ID,Created_Date,Updated_Date)
SELECT F.City_ID,F.Product_ID,F.Time_ID,F.Created_Date,F.Updated_Date
FROM [EXERCISE].[Fact_Sales] F
JOIN deleted D
ON F.Fact_Sales_ID = D.Fact_Sales_ID
PRINT 'Deleted row entered.'
It is not working. Reason I suspect is- the row is being deleted from the table before the trigger is fired and thats why it is not able to join and hence not inserting any records. But when I debug and print messages I can see that trigger happens before deletion.
Can someone please explain me how exactly does this trigger work?
You are deleting rows from the [EXERCISE].[Fact_Sales] table, yet in your trigger you are joining to this table, expecting the records to still be there - they are not.
At that point, the Deleted pseudo-table has the same schema as the [EXERCISE].[Fact_Sales] table, but with the rows you have just deleted in it. Instead of trying to join back to a table for rows you know aren't there any more, just use the Deleted table directly for your insert:
CREATE TRIGGER [EXERCISE].[delete_trigger]
ON [EXERCISE].[Fact_Sales]
AFTER DELETE
AS
INSERT INTO [EXERCISE].[Fact_Sales_Audit](City_ID,Product_ID,Time_ID,Created_Date,Updated_Date)
SELECT D.City_ID,
D.Product_ID,
D.Time_ID,
D.Created_Date,
D.Updated_Date
FROM deleted D
The trigger does fire after the delete on the main table, as the AFTER DELETE syntax implies. It fires somewhere between when the delete statement is executed, and before the control is returned to the user. It takes place in the same transaction - e.g. if the delete was rolled back for whatever reason, the inserts performed by the trigger would also be rolled back.
You should simplify your trigger definition to fetch just deleted row(s) from virtual table DELETED. What will happen is your deleted rows will be temporarily stored in that table and then will be inserted into audit table.
NB! Be sure you have set primary key on your Fact_Sales table.
CREATE TRIGGER [delete_trigger] ON [Fact_Sales]
FOR DELETE
AS
INSERT INTO [Fact_Sales_Audit](Fact_Sales_Id,City_ID,Product_ID,Time_ID,Created_Date,Updated_Date)
SELECT Fact_Sales_Id,City_ID,Product_ID,Time_ID,Created_Date,Updated_Date
FROM DELETED
I have a trigger that runs after the update record in the table A, add records to a table B
Now the table B has a trigger that works to ensure that the values entered are correct, when there is a problem with it, the role of a trigger table B is to prevent the entry record (I can not use a unique index because the conditions are in other tables), but I want to avoid only the current record entry, as well as not to prevent the update is done in Table A and not the all good records in this transaction.
the ROLLBACK function is canceling all open transactions.
I have a trigger that inserts a record into a diff table but I need to get that record that was inserted inside the trigger, how do I do it? There is no identity field, only account_nbr that is generated by a separate trigger on the insert table.
I don't know if there is sql statements to retrieve a row that was just inserted.
DB is Sql Server 2008.
The OUTPUT clause will give you back the records you have just inserted: http://msdn.microsoft.com/en-us/library/ms177564.aspx
If you mean the rows inserted before the trigger invoked, they are in the inserted pseudo-table.
If a run an INSERT INTO statement that triggers an INSERT AFTER trigger. What table/row(s) does the inserted and deleted objects represent in the trigger? For example,
INSERT INTO Person.person (personID, name) VALUES (1, 'robert')
CREATE TRIGGER myTrigger
ON Person.person
AFTER INSERT AS
BEGIN
insert into Person.PersonMovies (personID, movieID)
select inserted.personID from inserted _--i know the code is incomplete, but i'm curious only about the inserted part._
END
I'm confused as to what records are held by the inserted table. Would it be the records in the insert statement that triggered the trigger or the Person.PersonMovies table?
Yes, the inserted/deleted tables gives your trigger code access to the records changed by the statement that caused (triggered) the trigger. Also remember that your statements could have effected multiple rows, so your deleted or inserted tables could have multiple records.
The rows in the pseudotables inserted and deleted are based on the table defined in you ON clause.
The Inserted table holds the rows from the original Insert statement that caused the trigger to fire.
See also this MSDN article.
The inserted and deleted pseudotables hold one record for each row in the table that was created or deleted by the statement that fired the trigger. For an update, the deleted table holds the old version of the records, and the inserted table holds the new. The schema of the pseudotables matches the actual table.