I have a Products table with columns QtySold_Day and QtySold_Yesterday, which contain information about the quantity of sold products today and yesterday respectively.
I want to create a trigger that moves every single value from the QtySold_Day column to the QtySold_Yesterday whenever there's an attempt to update the QtySold_Day column.
This is what I already have:
create or alter trigger UpdateQuantity
on Products
instead of update
as
declare #x int
set nocount on
while (#x < ##ROWCOUNT)
begin
update Products
set QtySold_Day = QtySold_Yesterday
where (ProductID = #x)
end
I'd like to know how can I finish the trigger for it to work as intended.
SQL is a set based language, so you should always attempt set based operations. Inside a trigger you have access to a pseudo table called Inserted which has the new details of the update. You can therefore update all the relevant records in one go.
As commented you are probably going to need a way to avoid copying the values over if the record is updated multiple times - so I have added a check to ensure it only happens once. That might not be quite the behaviour you want so if you clarify we can tweak it.
Do you really want an INSTEAD OF trigger? Because that will capture ALL updates to this table, and for the most part do nothing.
UPDATE Products SET
QtySold_Day = QtySold_Yesterday
WHERE ProductID IN (SELECT ID FROM Inserted)
-- Only update once
AND QtySold_Yesterday IS NULL;
Related
CREATE OR ALTER TRIGGER CheckQuantity
ON dbo.Products
AFTER UPDATE
AS
BEGIN
UPDATE dbo.Products
SET Product_ReOrder = 1
FROM Inserted i
WHERE i.Product_ID = dbo.Products.Product_ID
AND i.Product_QOH < 5;
I am not getting a syntax error
syntax error near ;
This is referring to the ; at the end of the code.
Not 100% sure what you're trying to do - you're not giving us much to go on, either!
I'm assuming you mean you want to set a column called Product_ReOrder in your table to 1 if another column Product_QOH is less than 5 - correct?
In that case - use a trigger something like this:
CREATE OR ALTER TRIGGER CheckQuantity
ON dbo.Products
AFTER UPDATE
AS
BEGIN
UPDATE dbo.Products
SET Product_ReOrder = 1
FROM Inserted i
WHERE i.PrimaryKeyColumn = dbo.Products.PrimaryKeyColumn
AND i.Product_QOH < 5;
END
The trigger will fire after an UPDATE, and Inserted will contain all rows (can and will be multiple rows!) that have been updated - so I'm assuming you want to check the quantity on those rows.
I'm joining the base table (dbo.Products) to the Inserted pseudo table on the primary key column of your table (which we don't know what it is - so you need to adapt this as needed), and I'm setting the Product_ReOrder column to 1, if the Products_QOH value is less than 5.
Your line of code
Select #QOH = (select Product_QOH from inserted)
has a fatal flaw of assuming that only one row was updated - this might be the case sometimes - but you cannot rely on that! Your trigger must be capable of handling multiple rows being updated - because the trigger is called only once, even if 10 rows are updated with a command - and then Inserted will contain all those 10 updated rows. Doing such a select is dangerous - you'll get one arbitrary row, and you'll ignore all the rest of them ....
Is that what you're looking for?
I'm unclear what you were thinking when you wrote this code, or what template you were basing off, but there are many syntax errors.
It seems you probably want something like this:
The update() function only tells us if that column was present in the update statement, not if anything was actually changed.
We need to check if we are being called recursively, in order to bail out.
We also check if no rows have been changed at all, and bail out early
Note how inserted and deleted are compared to see if any rows actually changed. This also deals correctly with multiple rows.
We then need to rejoin Products in order to update it.
create or alter trigger CheckQuantity
on Products
after update
as
set nocount on;
if not(update(Products_QOH))
or TRIGGER_NESTLEVEL(##PROCID, 'AFTER', 'DML') > 1
or not exists (select 1 from inserted)
return; -- early bail-out
update p
set Product_ReOrder = 1
from Products p
join (
select i.YourPrimaryKey, i.Products_QOH
from inserted i
where i.Product_QOH < 5
except
select d.YourPrimaryKey, d.Products_QOH
from deleted d
) i on i.YourPrimaryKey = p.YourPrimaryKey;
However, I don't understand why you are using a trigger at all.
I strongly suggest you use a computed column for this instead:
ALTER TABLE Products
DROP COLUMN Product_ReOrder;
ALTER TABLE Products
ADD Product_ReOrder AS (CASE WHEN Product_QOH < 5 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END);
I need to update a column in table after any record is added in same table
Here is my sql code
CREATE TRIGGER [dbo].[EmployeeInsert]
ON [dbo].[APP_Employees]
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
DECLARE #EmployeeID AS bigint
SELECT #EmployeeID = ID FROM inserted
UPDATE [dbo].[APP_Employees]
SET [EmployeeTotalNumberOfAnnualLeave] = [EmployeeBalanceTheInitialNumberOfDaysOfAnnualLeaveIn]
WHERE ID=#EmployeeID
END
GO
and showing error
Msg 2714, Level 16, State 2, Procedure EmployeeInsert, Line 17
There is already an object named 'EmployeeInsert' in the database.
The error you're getting is because you have that trigger already, in your database. So if you want to create it again, you need to first drop the existing trigger (or use ALTER TRIGGER instead of CREATE TRIGGER to modify the existing trigger).
BUT: your fundamental flaw is that you seem to expect the trigger to be fired once per row - this is NOT the case in SQL Server. Instead, the trigger fires once per statement, and the pseudo table Inserted might contain multiple rows.
Given that that table might contain multiple rows - which one do you expect will be selected here??
SELECT #EmployeeID = ID FROM inserted
It's undefined - you might get the values from arbitrary rows in Inserted.
You need to rewrite your entire trigger with the knowledge the Inserted WILL contain multiple rows! You need to work with set-based operations - don't expect just a single row in Inserted !
-- drop the existing trigger
DROP TRIGGER [dbo].[EmployeeInsert]
GO
-- create a new trigger
CREATE TRIGGER [dbo].[EmployeeInsert]
ON [dbo].[APP_Employees]
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
-- update your table, using a set-based approach
-- from the "Inserted" pseudo table which CAN and WILL
-- contain multiple rows!
UPDATE [dbo].[APP_Employees]
SET [EmployeeTotalNumberOfAnnualLeave] = i.[EmployeeBalanceTheInitialNumberOfDaysOfAnnualLeaveIn]
FROM Inserted i
WHERE [dbo].[APP_Employees].ID = i.ID
END
GO
I want to copy the contents of a column into another column in the same table. Therefore, I created this trigger:
ALTER TRIGGER [dbo].[kennscht_copy_to_prodverpt]
ON [dbo].[Stammdaten]
AFTER INSERT
AS
UPDATE Stammdaten
SET PRODVERPT = (SELECT KENNSCHT FROM INSERTED)
WHERE SNR = (SELECT SNR FROM INSERTED);
But when I use an UPDATE on the table to update KENNSCHT to a different value, PRODVERPT is not updated as well. Now, you could argue that is because the trigger is on AFTER INSERT and not AFTER UPDATE, but when I change it so it's triggered by UPDATE and INSERT, whenever I update any row, I get an error message from SQL Server
Cannot update row because it would make the row not unique or update multiple rows (2 rows) [sic]
What is going on here? Either the trigger doesn't do anything, or it's messing up the whole table, making it un-updateable.
Update: I also tried the following trigger:
UPDATE s
SET s.PRODVERPT = i.KENNSCHT
FROM Stammdaten s
INNER JOIN INSERTED i ON i.SNR = s.SNR;
But it has exactly the same behaviour. If I use only AFTER INSERT, nothing changes and if I use AFTER INSERT, UPDATE I get the error message above.
Update 2: There are no multiple rows in the table, I already checked that because I thought it might be connected to the issue.
If you run this trigger as an AFTER UPDATE trigger, it runs recursively, since it always issues another UPDATE statement against the same table, which leads to another execution of the trigger.
To work around this, you either need to make the update trigger an INSTEAD OF UPDATE trigger or test if the KENNSCHT column was modified at all. For the latter you can use the UPDATE() function like this:
ALTER TRIGGER [dbo].[kennscht_copy_to_prodverpt_after_update]
ON [dbo].[Stammdaten]
AFTER UPDATE
AS
BEGIN
SET NOCOUNT ON
IF (UPDATE(KENNSCHT))
BEGIN
UPDATE s
SET s.PRODVERPT = i.KENNSCHT
FROM Stammdaten s
INNER JOIN INSERTED i ON i.SNR = s.SNR
END
END
I need a SQL trigger that would zero pad a cell whenever its inserted or updated. Was curious if its best practice to append two strings together like I'm doing in the update command. Is this be best way to do it?
CREATE TRIGGER PadColumnTenCharsInserted ON Table
AFTER INSERT
AS
DECLARE
#pad_characters VARCHAR(10),
#target_column NVARCHAR(255)
SET #pad_characters = '0000000000'
SET #target_column = 'IndexField1'
IF UPDATE(IndexField1)
BEGIN
UPDATE Table
SET IndexField1 = RIGHT(#pad_characters + IndexField1, 10)
END
GO
Your padding code looks fine.
Instead of updating every row in the table like this:
UPDATE Table
update just the row that triggered the trigger:
UPDATE updated
Also, you've still got some extraneous code -- everything involving #target_column. And it looks like you're not sure if this is an INSERT trigger or an UPDATE trigger. I see AFTER INSERT and IF UPDATE.
Two questions:
What are you doing with #target_column? You declare it and set it with a column name, but then you never use it. If you intend to use the variable in your subsequent SQL statements, you may need to wrap the statements in an EXECUTE() or use sp_executesql().
The syntax "UPDATE Table..." is OK for your update statement assuming that "Table" is the name of the table you are updating. What seems to be missing is a filter of some kind. Or did you really intend for that column to be updated for every row in the whole table?
One way to handle this would be to declare another variable and set it with the PK of the row that is updated, then use a where clause to limit the update to just that row. Something like this:
DECLARE #id int
SELECT #id = Record_ID FROM INSERTED
-- body of your trigger here
WHERE Record_ID = #id
I like your padding code. It looks good to me.
Here is one very interesting problem. I am using SQL Server 2008.
I have two triggers on one common table say 'CommonTable'. one trigger is on update and other one is on insert/update/delete.
In first trigger "Trigger1", I do the checks/rollback sometime change the new inserted value based on business logic.
here is sample code
-
CREATE TRIGGER [dbo].[Trigger1] ON [dbo].[CommonTable]
FOR UPDATE
UPDATE [CommonTable]
SET
[StatusCode] = 'New Value'
WHERE
[RecId] = 'rec id value'
In second trigger "Trigger2", I store the new inserted/deleted/updated value from 'CommonTable' table to another table 'CommonTable_History' for history tracking purpose.
here is sample code
-
CREATE TRIGGER [dbo].[Trigger2] ON [dbo].[CommonTable]
FOR INSERT, UPDATE, DELETE
--based on logic read the value from DELETED or INSERTED table and store in other table.
SELECT #RowData = (SELECT * FROM DELETED AS [CommonTable] WHERE [RecId] = #RowRecId FOR XML AUTO, BINARY BASE64 , ELEMENTS)
--and then insert #RowData in 'CommonTable_History' table.
With the help of 'sp_settriggerorder', I have set the order of execution of these triggers, so first "Trigger1" get executed and then "Trigger2".
Second trigger "Trigger2" works well for insert/delete values. It works fine for new inserted value if new inserted values has not been changed by first trigger "Trigger1".
But if in some cases, inserted values has been changed in "Trigger1". say [StatusCode] = 'New Value' and old values was 'Old Value' then "Trigger2" still store the 'Old Value' instead of 'New Value'.
Why because "Trigger1" change the value but that value still has not been store in database and before that "Trigger2" get executed on Insert.
Now my requirement is, here I want to store "New Value".
So I thought, lets make "Trigger2" to use "AFTER" keywords. But "FOR" and "AFTER" behave same could not solve the problem.
Then I thought, lets make "Trigger2" to use "INSTEAD OF" keyword. But "INSTEAD OF" gives following error
"Cannot CREATE INSTEAD OF DELETE or INSTEAD OF UPDATE TRIGGER. This is because the table has a FOREIGN KEY with cascading DELETE or UPDATE."
I can not remove FOREIGN KEY with cascading DELETE or UPDATE for table 'CommonTable'.
Please let me know if you people have any other alternate solution.
-Vikram Gehlot
I think your second trigger needs to use the values from the actual table, not the inserted/deleted tables to populate the log table - inserted/deleted will always have the unaltered, original values, while your altered values will appear in the table. Make the second trigger an "After" trigger, so you will not have to use the sp_settriggerorder. Like this, for example:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER [dbo].[trg_Trig1]
ON [dbo].[TestTable]
FOR INSERT
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
update TestTable
set [value] = 10
where [value] = 25
END
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER [dbo].[trg_Trig2]
ON [dbo].[TestTable]
AFTER INSERT
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 log_TestTable
(id, description, [value])
select tt.id, tt.description, tt.[value]
from inserted i
LEFT JOIN TestTable tt
ON tt.id = i.id
END
It may not be the cleanest solution but can you simply combine the two triggers into one? That way both pieces of SQL would know about each other's changes.
Your second trigger appears to me as if it would not work properly is mulitple records are inserted in a set-based operations unloess you use a loop which is poor choice in a trigger. Fix that first!
Instead of select * from deleted, why not join the deleted or inserted table to the original table and take the values from there (except for the id value which you get from deleted or inserted, that should give you the most current values of all fileds and if you add other trigger logic later wil not break.