I am working on triggers using SQL server 2005. I have a trigger for a table which is after update. After declaring the variables, the code is like this.
if #isconfirmed_before = 0 and #isconfirmed_after = 1
begin
if #invite_userid <> ''
begin
select #points = points from dbo.InvitePoint where code = 'USR' and packageid = #packageid
INSERT INTO InviteCount
([userID]
,[joinMerchantID]
,[packageID]
,[points]
,[joinDate])
VALUES
(#invite_userid
,#merchantid
,#packageid
,#points
,getdate())
end
SET #alpha_numeric=''
SELECT #alpha_numeric=#alpha_numeric+CHAR(n) FROM
(
SELECT TOP 8 number AS n FROM master..spt_values
WHERE TYPE='p' and (number between 48 and 57 or number between 65 and 90)
ORDER BY NEWID()
) AS t
update merchant
set reg_code = #alpha_numeric
where merchantid = #merchantid
END
The last part of
update merchant
set reg_code = #alpha_numeric
where merchantid = #merchantid
This reg_code shoule be inserted only once when the row is inserted but it is changing every time there is an update to the table. How do i make it happen. Please help me, Thank you in advance!!
update merchant
set reg_code = #alpha_numeric
where merchantid = #merchantid
That code is executing every time there is an update, because you have no conditional flow preventing it from executing sometimes. If you want to only execute that given a certain condition, you'll need to wrap it in an IF block.
You say: "This reg_code shoule be inserted only once when the row is inserted but it is changing every time there is an update to the table." Why is that in an AFTER UPDATE trigger then? It looks like it should be in an AFTER INSERT trigger. Unless I am misunderstanding you.
OK you are very much in trouble with triggers. First you need to show the actual create trigger code. I suspect you don't have it set correctly to only fire on insert.
Next you need to assume that the trigger must be able to handle multiple record inserts. Anytime you are setting a value to a scalar variable in a trigger, you are probably doing something wrong. This can't be your whole trigger either because you haven't shown how you get the varible values.
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 am trying to write an update trigger on a table which would cause it to run an additional update statement only if a certain column has been changed, so far the trigger runs the update no matter what, hoping maybe someone can see what I am doing wrong here.
Here is the trigger.
ALTER TRIGGER [dbo].[StatusChangedUpdateTrigger]
ON [dbo].[Trans_Order]
AFTER UPDATE
AS
DECLARE #OldOrderStatusId INT, #NewStatusOrderId INT, #ERRNUM INT;
BEGIN
SET #OldOrderStatusId = (SELECT OrderStatusId FROM deleted);
SET #NewStatusOrderId = (SELECT OrderStatusId FROM inserted);
IF (#OldOrderStatusId != #NewStatusOrderId)
SET NOCOUNT ON;
UPDATE Trans_Order
SET StatusChanged = 1
WHERE Id = (SELECT ID FROM inserted)
END
For some reason this is running no matter what, I can never set StatusChanged to 0 as it will automatically flip it back to 1 even if the OrderStatusId hasn't changed. So my update statement is running no matter what, so I am guessing I am doing something wrong in the if statement.
Hmmmm . . . Your logic seems strange. I would expect:
UPDATE t
SET StatusChanged = 1
FROM Trans_Order t JOIN
Inserted i
ON t.id = i.id JOIN
Deleted d
ON t.id = d.id
WHERE i.OrderStatusId <> d.OrderStatusId;
You might need to take NULL values into account -- although your code does not.
Note that your code is just a bug waiting to happen, because it assumes that inserted and deleted have only one row.
The specific problem with your code is that it is really:
IF (#OldOrderStatusId != #NewStatusOrderId)
BEGIN
SET NOCOUNT ON;
END;
UPDATE Trans_Order
SET StatusChanged = 1
WHERE Id = (SELECT ID FROM inserted);
Your indentation has confused the logic. However, you should still use the set-based version so the trigger does not fail.
The correct way to approach your trigger is as follows:
create or alter trigger [dbo].[StatusChangedUpdateTrigger] on [dbo].[Trans_Order]
after update
as
set nocount on
if ##RowCount=0 return
if Update(OrderStatusId)
begin
update t
set statusChanged=1
from inserted i join deleted d on d.id=i.id and d.OrderStatusId != i.OrderStatusId
join Trans_Order t on t.id=i.id
end
Always test ##rowcount and return if no rows updated.
Always put set options before DML
As you are only looking to update if a specific column is updated you can test specifically for that and if the update statement that's run doesn't touch that column the trigger will not run.
This will correctly account for multiple rows being updated and only update those where the new value is different to the old value.
I have the following trigger, and I need that its only executed when one column value changes, is that possible?
ALTER TRIGGER [dbo].[TR_HISTORICO]
ON [dbo].[Tbl_Contactos]
AFTER UPDATE
AS
BEGIN
IF UPDATE (primerNombre) -- sólo si actualiza PRIMER NOMBRE
BEGIN
INSERT INTO [dbo].[Tbl_Historico] ([fecha],[idUsuario],[valorNuevo], [idContacto],[tipoHistorico] )
SELECT getdate(), 1, [dbo].[Encrypt]([dbo].[Decrypt](primerNombre)), [idContacto], 1
FROM INSERTED
END
END
The problem is the code is executed always even if another column changes
The problem is probably the way you are doing updates in your code. It may be updating every field and not only the one that changed.
In this case you need to check to see if there is a difference between the values in the inserted and deleted pseudo tables. Or fix your code so that it only updates what needs to be updated.
Comparing the value of primerNombre from the inserted and deleted tables
ALTER TRIGGER [dbo].[TR_HISTORICO] ON [dbo].[Tbl_Contactos]
AFTER UPDATE AS
BEGIN
INSERT INTO [dbo].[Tbl_Historico] ([fecha],[idUsuario],[valorNuevo], [idContacto],[tipoHistorico] )
SELECT getdate(), 1, [dbo].[Encrypt]([dbo].[Decrypt](i.primerNombre)), i.[idContacto], 1
FROM INSERTED i
inner join deleted d
on i.idContacto = d.idContacto
where i.primerNombre <> d.primerNombre
END
If primerNombre is nullable, the where will need to handle null comparisons as well.
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.
I've got a table where I need to auto-assign an ID 99% of the time (the other 1% rules out using an identity column it seems). So I've got a stored procedure to get next ID along the following lines:
select #nextid = lastid+1 from last_auto_id
check next available id in the table...
update last_auto_id set lastid = #nextid
Where the check has to check if users have manually used the IDs and find the next unused ID.
It works fine when I call it serially, returning 1, 2, 3 ... What I need to do is provide some locking where multiple processes call this at the same time. Ideally, I just need it to exclusively lock the last_auto_id table around this code so that a second call must wait for the first to update the table before it can run it's select.
In Postgres, I can do something like 'LOCK TABLE last_auto_id;' to explicitly lock the table. Any ideas how to accomplish it in SQL Server?
Thanks in advance!
Following update increments your lastid by one and assigns this value to your local variable in a single transaction.
Edit
thanks to Dave and Mitch for pointing out isolation level problems with the original solution.
UPDATE last_auto_id WITH (READCOMMITTEDLOCK)
SET #nextid = lastid = lastid + 1
You guys have between you answered my question. I'm putting in my own reply to collate the working solution I've got into one post. The key seems to have been the transaction approach, with locking hints on the last_auto_id table. Setting the transaction isolation to serializable seemed to create deadlock problems.
Here's what I've got (edited to show the full code so hopefully I can get some further answers...):
DECLARE #Pointer AS INT
BEGIN TRANSACTION
-- Check what the next ID to use should be
SELECT #NextId = LastId + 1 FROM Last_Auto_Id WITH (TABLOCKX) WHERE Name = 'CustomerNo'
-- Now check if this next ID already exists in the database
IF EXISTS (SELECT CustomerNo FROM Customer
WHERE ISNUMERIC(CustomerNo) = 1 AND CustomerNo = #NextId)
BEGIN
-- The next ID already exists - we need to find the next lowest free ID
CREATE TABLE #idtbl ( IdNo int )
-- Into temp table, grab all numeric IDs higher than the current next ID
INSERT INTO #idtbl
SELECT CAST(CustomerNo AS INT) FROM Customer
WHERE ISNUMERIC(CustomerNo) = 1 AND CustomerNo >= #NextId
ORDER BY CAST(CustomerNo AS INT)
-- Join the table with itself, based on the right hand side of the join
-- being equal to the ID on the left hand side + 1. We're looking for
-- the lowest record where the right hand side is NULL (i.e. the ID is
-- unused)
SELECT #Pointer = MIN( t1.IdNo ) + 1 FROM #idtbl t1
LEFT OUTER JOIN #idtbl t2 ON t1.IdNo + 1 = t2.IdNo
WHERE t2.IdNo IS NULL
END
UPDATE Last_Auto_Id SET LastId = #NextId WHERE Name = 'CustomerNo'
COMMIT TRANSACTION
SELECT #NextId
This takes out an exclusive table lock at the start of the transaction, which then successfully queues up any further requests until after this request has updated the table and committed it's transaction.
I've written a bit of C code to hammer it with concurrent requests from half a dozen sessions and it's working perfectly.
However, I do have one worry which is the term locking 'hints' - does anyone know if SQLServer treats this as a definite instruction or just a hint (i.e. maybe it won't always obey it??)
How is this solution? No TABLE LOCK is required and works perfectly!!!
DECLARE #NextId INT
UPDATE Last_Auto_Id
SET #NextId = LastId = LastId + 1
WHERE Name = 'CustomerNo'
SELECT #NextId
Update statement always uses a lock to protect its update.
You might wanna consider deadlocks. This usually happens when multiple users use the stored procedure simultaneously. In order to avoid deadlock and make sure every query from the user will succeed you will need to do some handling during update failures and to do this you will need a try catch. This works on Sql Server 2005,2008 only.
DECLARE #Tries tinyint
SET #Tries = 1
WHILE #Tries <= 3
BEGIN
BEGIN TRANSACTION
BEGIN TRY
-- this line updates the last_auto_id
update last_auto_id set lastid = lastid+1
COMMIT
BREAK
END TRY
BEGIN CATCH
SELECT ERROR_NUMBER() AS ErrorNumber, ERROR_MESSAGE() as ErrorMessage
ROLLBACK
SET #Tries = #Tries + 1
CONTINUE
END CATCH
END
I prefer doing this using an identity field in a second table. If you make lastid identity then all you have to do is insert a row in that table and select #scope_identity to get your new value and you still have the concurrency safety of identity even though the id field in your main table is not identity.