I have a table that has a composite primary key made from 3 columns, let's say A, B, C. I want to create a trigger that on UPDATE will check that these three columns won't be changed. This is what I have so far, but it doesn't seem to work:
CREATE TRIGGER TableTrigger
ON Table
AFTER INSERT, UPDATE AS
BEGIN
IF (EXISTS (SELECT * FROM inserted) AND EXISTS (SELECT * FROM deleted))
BEGIN
-- Update Operation
IF (SELECT COUNT(*) FROM inserted WHERE A IS NOT NULL OR B IS NOT NULL OR C IS NOT NULL) > 0
BEGIN
RAISERROR('Error, you cannot change Primary Key columns', 16, 1)
ROLLBACK
RETURN
END
END
I was expecting that if I update some values in a table, in inserted the values for the columns I don't update to be NULL, but it's not like that. I read somewhere that I need to look both in inserted and deleted to see if these values changed. So my question is this, can I check this without using a cursor?
Thank you.
You could do
CREATE TRIGGER TableTrigger
ON Table
AFTER UPDATE AS
BEGIN
IF UPDATE(A) OR UPDATE(B) OR UPDATE(C)
BEGIN
RAISERROR('Error, you cannot change Primary Key columns', 16, 1)
ROLLBACK
RETURN
END
END
Or deny update permissions on those columns.
Both approaches would deny any attempt to update the PK columns irrespective of whether or not the values actually change. SQL Server does not have row level triggers and unless there is an IDENTITY column in the table (guaranteed immutable) there is no reliable way to tell in a trigger if the PK was actually updated.
For example the INSERTED and DELETED tables in an UPDATE trigger on the table below would be identical for both the UPDATE statements.
CREATE TABLE T(C INT PRIMARY KEY);
INSERT INTO T VALUES (1),(-1)
/*Both values swapped*/
UPDATE T SET C = -C
/*Both values left the same*/
UPDATE T SET C = C
Related
After searching many pages I still can't find the answer about re-inserting deleted rows in the same table - not another table.
I have a table named timetable with the primary key made up from 3 columns Schoolcode, Year, Term.
I need for some reason need to insert deleted rows into the same table.
I get the error
Violation of PRIMARY KEY constraint
with the following trigger
ALTER TRIGGER [dbo].[AFTER_delete_]
ON [dbo].timetable
AFTER delete
AS
BEGIN
IF EXISTS (SELECT * FROM deleted)
BEGIN
INSERT INTO timetable
SELECT *
FROM deleted A
WHERE NOT EXISTS (SELECT 1 FROM timetable B
WHERE B.Schoolcode = A.Schoolcode
AND B.Year = A.Year
AND B.Term = A.Term);
END
END
thanks any way.I test the code below and that did work.
ALTER TRIGGER [dbo].[Instead_OfDelSert_Status]
ON [dbo].[Status]
INSTEAD OF delete,insert
AS
BEGIN
PRINT 'You must disable or delete Trigger Instead_OfDelSert_Status to insert or
delete rows!'
END
I'm trying to create a trigger that will prevent a user from inserting to or updating the quantity in my orderLines table if the amount is greater than the quantity on the products table.
Is there a way to do it in a single trigger or do I have to create to separate ones for both insert and update actions?
Below is how my trigger starts:
CREATE TRIGGER OrdersLines_ITrig
ON ordersLines
FOR INSERT
AS
Depends on the BEGIN/END blocks:
Triggers have special INSERTED and DELETED tables to track "before" and "after" data. So you can use something like IF EXISTS (SELECT * FROM DELETED) to detect an update. You only have rows in DELETED on update, but there are always rows in INSERTED.
CREATE TRIGGER dbo.TriggerName
ON dbo.TableName
AFTER INSERT, UPDATE
AS
BEGIN
SET NOCOUNT ON;
IF EXISTS (SELECT * FROM inserted) AND EXISTS (SELECT * FROM deleted)
BEGIN
----Do update
END;
IF EXISTS (SELECT * FROM Inserted) AND NOT EXISTS (SELECT * FROM deleted)
BEGIN
-----Do insert
END;
END
This is a simple requirement you can handle using CHECK CONSTRAINT itself. If you are defining trigger, you have to properly rollback the transaction. Have proper error message etc. You can simply have a check constraint, which will do all these things for you.
I would suggest you to do below steps:
Create a user defined function, which returns TRUE or FALSE, based on the quantity in the Product table.
CREATE FUNCTION CheckQuantity(#productID INT)
RETURNS BIT
AS
BEGIN
---LOGIC
END
Leverage the user defined function in the CHECK constraint.
ALTER TABLE OrderLines ADD CONSTRAINT CHK_Quantity CHECK( dbo.CheckQuantity(ProductId) = = 1)
In my SQl Server I have a table of around 40 attributes/columns. There is a daily load which might update any of these columns. I want to capture the changes in these columns in a separate table with a reason code column telling which column value changed. There might be instances where more than one column value might get changed in a single daily load, in that case the changed log table should capture all these changes separately in rows with each row depicting the individual change.
For Example:
TableA(column1(pk),column2,column3,column4)
values(1,100,ABC,999)
After update:
TableA(column1(pk),column2,column3,column4)
values(1,100,ACD,901)
The corresponding change log table should have two entries:
TabChangeLog(column1,before,after,reason);
values(1,ABC,ACD,'column3 changed')
values(1,999,901,'column4 changed')
I tried implementing this through triggers but am not able to figure out a way to separate each of these changes in separate rows when there are more than one changes. Please help
You need to create a trigger like :
create trigger trigger_name
instead of update as
if update(column1)
begin
insert into TabChangeLog
select inserted.column1, inserted.column3, deleted.column3, 'column3', 'update/change'
from inserted i inner join deleted d
on i.column1 = d.column2
end
if update(column2)
begin
insert into TabChangeLog
select inserted.column1, inserted.column2, deleted.column2, 'column2', 'update/change'
from inserted i inner join deleted d
on i.column1 = d.column2
end
...
https://www.tutorialgateway.org/instead-of-update-triggers-in-sql-server/
Microsoft SQL Server 2016 has a thing called Temporal Tables which would probably simplify your job a lot. It lets you rewind a dataset through time to see the changes:
https://learn.microsoft.com/en-us/sql/relational-databases/tables/temporal-tables?view=sql-server-2017
If you don't want to go that route and use triggers instead. UPDATE triggers have two tables inserted and deleted that let you know what the row state was before and after.
*Edit: These are tables so you have to use SELECT INTO etc to interact with them you can't do conditional logic (if /else)
CREATE TABLE [dbo].[Table1](
[Id] [int] NOT NULL,
[Tail] [int] NOT NULL,
CONSTRAINT [PK_Table1_1] PRIMARY KEY CLUSTERED
(
[Id] ASC
)
)
CREATE TABLE Table1_Audit
(
Audit varchar(100)
)
--drop trigger Table1_OnUPDATE
CREATE TRIGGER Table1_OnUPDATE
ON dbo.Table1
AFTER UPDATE
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for trigger here
INSERT INTO Table1_Audit ([Audit])
select CONCAT('Tail changed to' ,inserted.Tail,' for pk Id=',inserted.Id) from inserted inner join
deleted on inserted.Id = deleted.Id --pk must be the same
where
inserted.Tail <> deleted.Tail --field x must be different
END
GO
--truncate table Table1_Audit
--update Table1 set Tail = 5
select * from Table1_Audit
I need to control table values uniqueness. It cannot be done by an index or a constraint (error message must show data from another table). I thought of after trigger but since it fires after the insert the below trigger will fire even if values are unique.
--table
CREATE TABLE Names (Id IDENTITY(1,1) NOT NULL, Name VARCHAR(20) NOT NULL)
--first record
INSERT INTO Names VALUES ('John')
--trigger
CREATE TRIGGER [dbo].[Names_Insert_Trigger]
ON [dbo].[Names]
FOR INSERT, UPDATE
AS
SET NOCOUNT ON
IF EXISTS (SELECT Name
FROM inserted
WHERE EXISTS (SELECT * FROM Names N JOIN inserted ON N.Name=inserted.Name))
BEGIN
RAISERROR('This name is already registered in file XYZ.', 16, 1)
ROLLBACK TRAN
SET NOCOUNT OFF
RETURN
END
SET NOCOUNT OFF
--I add another record with different value and the trigger fires
INSERT INTO Names VALUES ('Steven')
I also thought of an instead of insert trigger but the actual table has identity set and will likely get new columns in the future which would require updating the trigger code at each change so I can't use the below code:
CREATE TRIGGER [dbo].[Names_Insert_Trigger]
ON [dbo].[Names]
INSTEAD OF INSERT
AS
SET NOCOUNT ON
IF EXISTS (SELECT Name
FROM inserted
WHERE EXISTS (SELECT * FROM Names N JOIN inserted ON N.Name=inserted.Name))
BEGIN
RAISERROR('This name is already registed in file XYZ.', 16, 1)
ROLLBACK TRAN
SET NOCOUNT OFF
RETURN
END
ELSE
INSERT INTO Names
SELECT * FROM inserted
SET NOCOUNT OFF
Any ideas how to solve it?
Regards,
Przemek
You can use an after trigger. Just use COUNT instead of EXISTS. You should still have a non-unique index on name to optimize performance and concurrency.
IF (SELECT COUNT(*)
FROM inserted AS i
JOIN dbo.Names AS N ON
N.Name = i.Name
GROUP BY N.Name
) > 1
BEGIN
RAISERROR...
END;
The real solution is to use the UNIQUE constraint to this problem, it's designed to solve it and it's much more performant and safer than a trigger for this usage. The error message is better built client-side and ignore the server genereated one, save for determining the exact reason.
But if you really want to follow the trigger route, use the AFTER version, but fix the query for detect duplicates:
SELECT * FROM (
SELECT Name
FROM Names
WHERE id NOT IN (SELECT id FROM inserted)
) PreviousNames
INNER JOIN inserted ON PreviousNames.Name = inserted.Name
(I'm just showing the query to check duplication that goes into the IF EXIST instruction, not the whole trigger).
It begins by creating a subquery that gets the names NOT being inserted (so that you don't get a false positive), then simply joins again to inserted to check if any value is in both tables.
There is an additional problem that can happen when using SNAPSHOT issolation level. In this mode, the trigger will NOT see the changes made by other connections, nor they'll be blocked until the trigger ends. I'm not quite familiar with the details, but will leave this article as reference and possible solutions: https://sqlserverfast.com/?s=snapshot+integrity
I have a simple details table like so:
listid
custid
status
last_changed
The primary key consists of both listid and custid.
Now I'm trying to setup a trigger that sets the last_changed column to the current datetime every time an insert or update happens. I've found lots of info on how to do that with a single PK column, but with multiple PKs it gets confusing on how to correctly specify the PKs from the INSERTED table.
The trigger has to work in SQL Server 2005/2008/R2.
Thanks for a working trigger code!
Bonus would be to also check if the data was actually altered and only update last_changed in that case but for the sake of actually understanding how to correctly code the main question I'd like to see this as a separate code block if at all.
Hmm.... just because the primary key is made up of two columns shouldn't really make a big difference....
CREATE TRIGGER dbo.trgAfterUpdate ON dbo.YourTable
AFTER INSERT, UPDATE
AS
UPDATE dbo.YourTable
SET last_changed = GETDATE()
FROM Inserted i
WHERE dbo.YourTable.listid = i.listid AND dbo.YourTable.custid = i.custid
You just need to establish the JOIN between the two tables (your own data table and the Inserted pseudo table) on both columns...
Are am I missing something?? .....
CREATE TRIGGER dbo.trgAfterUpdate ON dbo.YourTable
AFTER INSERT, UPDATE
AS
UPDATE dbo.YourTable
SET last_changed = GETDATE()
FROM Inserted i
JOIN dbo.YourTable.listid = i.listid AND dbo.YourTable.custid = i.custid
WHERE NOT EXISTS
(SELECT 1 FROM Deleted D Where D.listid=I.listid AND D.custid=i.custid AND (D.status=i.status)
Here i assuming that stasus column is not nullable. If yes, you should add additional code to check if one of columns is NULL
You can check every field in trigger by comparing data from inserted and deleted table like below :
CREATE TRIGGER [dbo].[tr_test] ON [dbo].[table]
AFTER INSERT, UPDATE
AS
BEGIN
DECLARE #old_listid INT
DECLARE #old_custid INT
DECLARE #old_status INT
DECLARE #new_listid INT
DECLARE #new_custid INT
DECLARE #new_status INT
SELECT #old_listid=[listid], #old_custid=[custid], #old_status = [status] FROM [deleted]
SELECT #new_listid=[listid], #new_custid=[custid], #new_status = [status] FROM [inserted]
IF #oldstatus <> #new_status
BEGIN
UPDATE TABLE table SET last_changed = GETDATE() WHERE [listid] = #new_listid AND [custid] = #new_custid
END
END