I need to write a trigger which prevents from inserting more than one record at the same time and also checks if the place is already in the database. Code compiles but it doesn't work as it should - it displays error message even if I try to add a non-existing address
Here's my code:
CREATE TRIGGER address_duplicate ON place
AFTER INSERT
AS
BEGIN
DECLARE #counter INT
SELECT #counter=COUNT(*) FROM place WHERE street IN (SELECT street FROM inserted) AND number IN(SELECT number FROM inserted)
AND city IN(SELECT city FROM inserted) AND postcode IN(SELECT postcode FROM inserted)
IF #counter>0
BEGIN
RAISERROR('This record is already in the database',1,1)
ROLLBACK
END
IF ##ROWCOUNT>1
BEGIN
RAISERROR('You can add only one record at the same time',1,2)
ROLLBACK
END
END
GO
Your logic of identifying duplicate place is not correct.
Try something like this:
select #counter= count(*) from place p join inserted n
where p.address=n.address and p.city=n.city and p.postcode=n.postcode
and p.number=n.number;
Also want you to know, using triggers to avoid duplicate can be very expensive.
Personally, I'd use a unique constraint and probably use TRY-CATCH when inserting, but if you really want to do it in a trigger, try this out:
CREATE TRIGGER address_duplicate ON place
INSTEAD OF INSERT
AS
BEGIN
DECLARE #newValue TABLE (ID INT);
IF ##ROWCOUNT > 1
BEGIN
RAISERROR('Insert cancelled. You can add only one record at the same time.',1,2);
END
ELSE
BEGIN
INSERT INTO place
OUTPUT inserted.ID INTO #newValue
SELECT *
FROM inserted
EXCEPT
SELECT *
FROM place
IF (SELECT 1 FROM #newValue) IS NULL
RAISERROR('Insert cancelled. This record is already in the database',1,1)
END
END
Related
I can detect duplicate records, but when I'm inserting new data it will detect it as a duplicate record even if doesn't already exist.
Here is my code:
ALTER TRIGGER [dbo].[SDPRawInventory_Dup_Trigger]
ON [dbo].[SDPRawInventory]
AFTER INSERT
AS
DECLARE #Year float,
#Month float,
#SDPGroup nvarchar(255);
SELECT
#Year = i.InvYear, #Month = i.InvMonth, #SDPGroup = i.SDPGroup
FROM inserted i;
IF (SELECT COUNT(*) FROM SDPRawInventory A
WHERE A.InvYear = #Year
AND A.InvMonth = #Month
AND A.SDPGroup = #SDPGroup) >= 1
BEGIN
RAISERROR ('Duplicate data', 16, 1)
ROLLBACK;
END
ELSE
BEGIN
INSERT INTO SDPRawInventory
SELECT * FROM inserted;
END
This is the table
And to clarify there is no primary key nor unique identifier.
If you are unable to put a constraint in place, then you need to handle the fact that Inserted may have multiple records. And because its an after insert trigger, you don't need to do anything if no duplicates are found because the records are already inserted.
ALTER TRIGGER [dbo].[SDPRawInventory_Dup_Trigger]
ON [dbo].[SDPRawInventory]
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
IF EXISTS (
SELECT 1
FROM dbo.SDPRawInventory S
INNER JOIN Inserted I ON
-- Test for a duplicate
S.InvYear = I.InvYear
AND S.InvMonth = I.InvMonth
AND S.SDPGroup = I.SDPGroup
-- But ensure the duplicate is a *different* record - assumes a unique ID
AND S.ID <> I.ID
)
BEGIN
THROW 51000, 'Duplicate data.', 1;
END;
END;
Note the simplified and modern error handling.
EDIT: And if you have no unique key, and no permission to add one, then you need an instead of trigger to only insert non-duplicates e.g.
ALTER TRIGGER [dbo].[SDPRawInventory_Dup_Trigger]
ON [dbo].[SDPRawInventory]
INSTEAD OF INSERT
AS
BEGIN
SET NOCOUNT ON;
-- Reject the entire insert if a single duplicate exists
-- Note if multiple records are inserted, some of which are duplicates and some of which aren't, they all get rejected
IF EXISTS (
SELECT 1
FROM dbo.SDPRawInventory S
INNER JOIN Inserted I ON
-- Test for a duplicate
A.InvYear = I.InvYear
AND A.InvMonth = I.InvMonth
AND A.SDPGroup = I.#SDPGroup
)
-- Test that Inserted itself doesn't contain duplicates
OR EXISTS (SELECT 1 FROM Inserted GROUP BY InvYear, InvMonth, SDPGroup HAVING COUNT(*) > 1)
BEGIN
THROW 51000, 'Duplicate data.', 1;
END;
INSERT INTO dbo.SDPRawInventory (SDP_SKU_DESC, WholeQty, InvYear, InvMonth, SDPGroup, invUOM, LooseQty)
SELECT SDP_SKU_DESC, WholeQty, InvYear, InvMonth, SDPGroup, invUOM, LooseQty
FROM Inserted I
WHERE NOT EXISTS (
SELECT 1
FROM dbo.SDPRawInventory S
-- Test for a duplicate
WHERE S.InvYear = I.InvYear
AND S.InvMonth = I.InvMonth
AND S.SDPGroup = I.SDPGroup
);
END;
Note: This doesn't do anything to handle existing duplicates.
This trigger is executed after the new records were inserted, so it will at least find the original records in the SELECT COUNT statement. Changing >= 1 into >= 2 can only partially fix this when inserting is guaranteed to occur one record as a time. Moreover, it will still fail when there were already multiple duplicated of the newly inserted record in the database before the insert.
You need to exclude the latest inserted records from the COUNT. But a better idea would probably be to add a UNIQUE constraint for preventing duplicates, so no trigger would be necessary.
If adding a constraint is not possible yet, you should initiate a clean-up process to eliminate the existing duplicates beforehand. Everything else is looks pretty flawed to me, since it is unlikely the current approach will ever bring the table into a state with no duplicates.
You are creating the infinite loop. You just have to remove the insertion part from your trigger.
ELSE
BEGIN
INSERT INTO SDPRawInventory
SELECT * FROM inserted;
END
This should not be in the trigger as trigger is called as part of insertion. you should not write actual insertion in to table in trigger.
Here is a trigger
CREATE TRIGGER [dbo].[CheckApplyId]
ON [dbo].[AppliedStudent_event] INSTEAD OF INSERT
AS
DECLARE #studentId INT
DECLARE #compReq_Id INT
BEGIN
SELECT #studentId = studentId
FROM INSERTED
SELECT #compReq_Id = compReq_Id
FROM INSERTED
IF EXISTS(SELECT StudentId,
compreq_id
FROM AppliedStudent_event
WHERE StudentId = #studentId
AND compreq_id = #compReq_Id)
BEGIN
ROLLBACK
PRINT 'User Already Applied'
END
END
When in insert a data into a table using command:
INSERT INTO AppliedStudent_event (StudentId, compreq_id)
VALUES (3026, 1)
Message is:
(1 row(s) affected)
But when I execute a sql command no data is inserted in the table.
Can you please tell why are you using trigger because you use only assign the variable #studentId and #compReq_Id from inserted table.
That's a broken trigger because inserted can contain multiple (or no) rows - so a statement like SELECT #ScalarVariable = column from inserted is always wrong.
And it's unnecessary since you can just place a UNIQUE constraint on the StudentId and compreq_id columns:
ALTER TABLE AppliedStudent_event
ADD CONSTRAINT UQ_Student_Events
UNIQUE (StudentId,compreq_id)
And it's further broken because you've specified it as an instead of trigger - that says that your code is going to be responsible for the actual insert - but your code doesn't actually do that. That's why no data ends up in the table.
If you insist on doing it as a trigger, it's actually tricky to get everything correct (that's why I'd really recommend the UNIQUE constraint). It'll end up being something like this:
CREATE TRIGGER [dbo].[CheckApplyId]
ON [dbo].[AppliedStudent_event] INSTEAD OF INSERT
AS
IF EXISTS(select
StudentId,compreq_id,COUNT(*)
from inserted
group by StudentId,compreq_id
HAVING COUNT(*) > 1)
OR EXISTS (select *
from inserted i
inner join
AppliedStudent_event e
on
i.StudentId = e.StudentId and
i.compreq_id = e.compreq_id)
BEGIN
ROLLBACK
PRINT 'User Already Applied'
END
ELSE
BEGIN
INSERT INTO AppliedStudent_event(StudentId,compreq_id /* Other columns? */)
SELECT StudentId,compreq_id /* And again, other columns */
FROM inserted
END
all id columns has auto_increment
In my trigger:
ALTER trigger [dbo].[mytrig]
on [dbo].[requests]
after INSERT, UPDATE
as
begin
declare #MyId1 int
set #MyId1 = (select Id from inserted)
declare #MyId2 int
declare #MyId3 int
if (select column1 from inserted) = 1
begin
insert into [dbo].[contracts] select column1,column2,column3 .... from inserted
set #MyId2 = SCOPE_IDENTITY()
insert into [dbo].[History] select column1,column2,column3 .... from inserted
set #MyId3 = SCOPE_IDENTITY()
insert into [dbo].[contracts_depts](Id_Contract ,column5) select #MyId2,column6 from request_depts where Id_request=#MyId1
insert into [dbo].[History_depts] (Id_InHistory,column5) select #MyId3,column6 from request_depts where Id_request=#MyId1
end
end
#MyId1 returns value only after update but not after insert. Do I have to use scope_identity() or something ?
Your main issue is: you're assuming the triggers is called once per row - that is NOT the case!
The trigger is called once per statement, and if your statement affects multiple rows, the Inserted pseudo table will contain multiple rows - so your statement here
set #MyId1 = (select Id from inserted)
really isn't going to work - it will select one arbitrary row (out of however many there are).
You'll need to rewrite your trigger to take this fact into account! Assume that Inserted contains 100 rows - how do you want to deal with that? What are you trying to achieve? Triggers don't return values - they will record into an audit table, or update other rows, or something like that ....
I wrote this trigger below. it is generating Error at COUNT(*) From. I want that when any row inserts into table 'Users' with this trigger currently present folders in Assignments should assign to User.
For Example: I add new row to table Users suppose userD. Then with the help of this trigger Present folders like folderA, folderB, folderC should assign to userD with folder right Visible by default. I have written this Trigger below but it is givig Error at Count(*) From
CREATE TRIGGER Trigger_Insert ON Users
FOR INSERT
AS
declare #userid int;
declare #username nvarchar(50);
declare #useremail nvarchar(50);
declare #userpassword nvarchar(50);
select #userid=i.user_id from inserted i;
select #username=i.user_name from inserted i;
select #useremail=i.user_email from inserted i;
select #userpassword=i.user_password from inserted i;
DECLARE #intFlag INT
SET #intFlag =1
WHILE (#intFlag <=COUNT(*) FROM Assignments;) // Error Here
BEGIN
insert into UAssignment_Rights(
ua_rights_id,ua_rights_name,assignment_id,user_id)
values(#userid,'Visible','','');
SET #intFlag = #intFlag + 1
PRINT 'AFTER INSERT trigger fired.'
END
GO
Can you please help me to solve this issue.
Answer updated to comply with info from comments.
My point is that most of the times you do not need loops or cursor in Sql Server. Usually set based approach is simpler and faster. In this case you might use form of insert that does not insert fixed values but rather result of select.
CREATE TRIGGER Trigger_Insert ON Users
FOR INSERT
AS
-- this is mandatory in trigger - you do not want ##rowcount reported to applications
-- to change as a result of statement in trigger (all of them, including set and select)
set nocount on
-- You can simply take assignment_id directly from Assignments table
insert into UAssignment_Rights(ua_rights_name, assignment_id, user_id)
select 'Visible', a.assignment_id, i.user_id
from Inserted i
cross join dbo.Assignments a
PRINT 'AFTER INSERT trigger fired.'
GO
P.S. cartesian product is result of join without join condition. Meaning that returned rows are all possible cobinations of each row from left table with each row from right table.
COUNT(*) should only be used as part of a SELECT or HAVING statement, see MSDN for more information on aggregate functions.
If Assignments will not change as part of the WHILE loop, try replacing...
WHILE (#intFlag <=COUNT(*) FROM Assignments;) // Error Here
With...
DECLARE #AssignmentsCount INT
SELECT #AssignmentsCount = COUNT(*) FROM Assignments
WHILE #intFlag <= #AssignmentsCount
This means that the COUNT(*) is only done once.
However, if the number of Assignments could change during the loop, the replace it with...
WHILE #intFlag <= (SELECT COUNT(*) FROM Assignments)
SQL Server 2008
I have trigger defined on
TABLE_A for 'INSTEAD OF INSERT' and TABLE_B for 'INSTEAD OF INSERT'.
Both the triggers perform merge with the inserted table.
TABLE_A insert is done by user/code and is working well, trigger for insert is fired.
I have Stored procedure SP_1 inside TABLE_A TRIGGER.
SP_1 Inserts data from TABLE_A into TABLE_B based on some conditions.
But the problem is when the stored procedure (SP_1) is inserting data, the trigger on TABLE_B is not fired and the data is just inserted as it is.
So can stored procedure inserts fire triggers?
Pseudo-code
ALTER TRIGGER [dbo].[trgtable_AInsert] ON [dbo].[TABLE_A]
Instead of INSERT
AS
BEGIN
SET NOCOUNT ON;
IF exists(SELECT * FROM INSERTED)
BEGIN
MERGE
.......
...........
..............
end
EXEC SP_1 #employee_id
end
ALTER TRIGGER [dbo].[trgtableB_Insert] ON [dbo].[TABLE_B]
Instead of INSERT
AS
BEGIN
SET NOCOUNT ON;
IF exists(SELECT * FROM INSERTED)
BEGIN
MERGE
.......
...........
..............
end
end
ALTER PROCEDURE [dbo].[SP_1] #employeeid int
AS
BEGIN
BEGIN TRANSACTION
insert into TABLE_B
.......
...........
..............
from TABLE_A
where employee_ID is #employeeid
COMMIT TRANSACTION
END
Yes triggers can fired by stored procedure inserts!
But I think the problem is that you should try to use AFTER instead of INSTEAD OF triggers in this case. Becasue I can't see all of your code, but it is possible, that the insert is not done because you overrided it in the Instead Of triggers. With AFTER triggers you should have no problems with firing the second trigger.
This is too big for a comment, and needs formatting, so posting as an "answer".
Yes, triggers will fire in this case. Taking your example and slightly modifying it (note the warnings though):
create table Table_A (ID int not null)
go
create table Table_B (ID int not null)
GO
CREATE PROCEDURE [dbo].[SP_1] #employeeid int
AS
BEGIN
BEGIN TRANSACTION
insert into TABLE_B (ID)
SELECT ID from TABLE_A
where ID = #employeeid
COMMIT TRANSACTION
END
GO
Creating the triggers:
CREATE TRIGGER [dbo].[trgtable_AInsert] ON [dbo].[TABLE_A]
Instead of INSERT
AS
BEGIN
SET NOCOUNT ON;
IF exists(SELECT * FROM INSERTED)
BEGIN
MERGE
into Table_A a
using inserted i on a.id = i.id
when not matched then insert (ID) values (i.id);
end
--Wrong code, just for example
declare #employee_id int
select #employee_id = ID from inserted --BAD CODE, Ignores multiple rows
EXEC SP_1 #employee_id
end
GO
CREATE TRIGGER [dbo].[trgtableB_Insert] ON [dbo].[TABLE_B]
Instead of INSERT
AS
BEGIN
SET NOCOUNT ON;
IF exists(SELECT * FROM INSERTED)
BEGIN
MERGE
into Table_B b
using inserted i on b.id = i.id
when not matched then insert (ID) values (i.id+5);
end
end
GO
And executing a trial insert into Table_A:
insert into Table_A (ID) values (1),(2)
select * from Table_B
On my machine, at the present time, I get a final result of a single row with the value "7". Others may run this sample and get the result "6", because triggers only run once per statement, rather than once per row. But as you can see, both triggers have fired.
As i previously mentioned in the comments #András Ottó
Merge
using(... = "column with possible null values" AND
... = ... AND
... = ...
)
of merge was not working correctly and the records were always inserted.
1 = 1 and E=E and NULL=NULL is not true. (of-course sql 101)
I have overlooked this column and did not place where clause properly to get rid of null values so ended up inserting all the time. Fixing that everything ended up working.
Thanks for the help Every1. Cheers
Apologies.
I'm not going to mark it answered because it is purely my mistake which was not fully mentioned in the question.