Instead of trigger before delete - sql-server-2005

suppose i have one instead of trigger for a table before delete. so i just want to know if i issue a delete then Instead of trigger will fire before delete ?
also tell me how to get deleted data from Instead of trigger before delete. can anyone show me with sample code.

It fires instead of the delete. If you don't implement it yourself nothing gets deleted. These triggers are usually used on Views not Tables.
CREATE TABLE T(
C INT IDENTITY(1,1) PRIMARY KEY,
D INT)
INSERT INTO T (D)
SELECT 1 UNION ALL SELECT 2
GO
CREATE TRIGGER tr ON T
INSTEAD OF DELETE
AS
BEGIN
PRINT 'Do Nothing'
END
GO
DELETE
FROM T
SELECT *
FROM T /*The 2 rows are still there*/
GO /*Implement the trigger*/
ALTER TRIGGER tr ON T
INSTEAD OF DELETE
AS
BEGIN
DELETE T
FROM T
JOIN DELETED D
ON T.C = D.C
END
GO
DELETE
FROM T
SELECT *
FROM T /*The 2 rows are now gone*/
DROP TABLE T

Related

Sql Trigger to add new row when table update

I am new to sql triggers and learning as developing triggers for asp.net application.i am having case where I need to first save table and then edit the same table - this edit create new row in different table but the the problem is every time I edit the table it create new row in different table I want to create row in different table for only first edit.
Dividing my problem for readability.
I have two tables:
Table A and table B
I have written trigger on table A that add row in table B.
Problem:
Every time I edit row in table A a new row get added to table B. (So every edit create new row)
Required result:
I want my trigger to add ONLY one row in table B for the first edit in table A but not for subsequent edits.
I am using update triggers.
Any example with code would be great
Thanks you much in advance .
Create TRIGGER [dbo].[triggerName] ON [dbo].[databaseName]
For Update
As
Begin
DECLARE #i int
DECLARE #d int
DECLARE #action char(6)
DECLARE #Car VARCHAR(20)
IF (##ROWCOUNT = 0) RETURN
SELECT #i = Count(*) From Inserted
SELECT #d = Count(*) From Deleted
SELECT #action = CASE
WHEN (#i <> 0) and (#d <> 0) THEN 'UPDATE'
WHEN (#i = 0) and (#d <> 0) THEN 'DELETE'
WHEN (#i <> 0) and (#d = 0) THEN 'INSERT'
End
SELECT #Car = A From inserted
IF #action = 'UPDATE' AND #Car in ('BMW')
Begin
INSERT INTO Tableb (c,d,f)
Select c,d,f from inserted
End
Your trigger has some flaws in it.
First, You don't need to test if it was fired because of update, insert or delete. The trigger is specified for update, so inserts and deletes will not fire it anyway.
Second, SELECT #Car = A From inserted will raise an error whenever you update more then one row in the table.
Third, As you said, this will insert a record in tableB for every update, while you want it to insert a record only for the first update done (I assume one for the first update on any row, so if you update row 1 then insert, update row 2 then another insert, and update row 1 again don't insert).
I would write it like this:
Create TRIGGER [dbo].[triggerName] ON [dbo].[tableName]
For Update
As
Begin
INSERT INTO Tableb (c,d,f)
Select c,d,f
from inserted i
left join Tableb t ON(i.c = t.c and i.d = t.d and i.f = t.f)
where t.id is null -- or some other non-nullable column
and i.a = 'BMW'
End
You can modify your SQL trigger to execute only after INSERT
CREATE TRIGGER dbo.myTable_Insert
ON dbo.myTable
AFTER INSERT
AS
It is possible to create SQL trigger to run after insert, update or delete as seen in the referred tutorial

UPDATE and INSERT should fire trigger only once

Is there any way to combine an update and an insert statements in a way that they fires a trigger only once?
I have one particular table that has (and currently needs) a trigger AFTER INSERT, UPDATE, DELETE. Now I want to update one row and insert another row and have the trigger fire only once for that.
Is this at all possible?
I already tried a MERGE-Statement without success: The trigger fires once for the update- and once for the insert-part.
Well, problem solved for me. I did NOT find a way to combine the statements into one fire-event of the trigger. But the trigger behaves in an interesting way, that was good enough for me: Both calls to the trigger do already have access to the fully updated data.
Just execute the following statements and you will see what I mean.
CREATE TABLE Foo (V INT)
GO
CREATE TRIGGER tFoo ON Foo AFTER INSERT, UPDATE, DELETE
AS
SELECT 'inserted' AS Type, * FROM inserted
UNION ALL
SELECT 'deleted', * FROM deleted
UNION ALL
SELECT 'actual', * FROM Foo
GO
DELETE FROM Foo
INSERT Foo VALUES (1)
;MERGE INTO Foo
USING (SELECT 2 AS V) AS Source ON 1 = 0
WHEN NOT MATCHED BY SOURCE THEN DELETE
WHEN NOT MATCHED BY TARGET THEN INSERT (V) VALUES (Source.V);
As a result, the trigger will be called twice for the MERGE. But both times, "SELECT * FROM Foo" delivers the fully updated data already: There will be one row with the value 2. The value 1 is deleted already.
This really surprised me: The insert-trigger is called first and the deleted row is gone from the data before the call to the delete-trigger happens.
Only the values of "inserted" and "deleted" correspond to the delete- or insert-statement.
You could try something like this:
The trigger would check for the existence of #temp table.
If it doesn't exist, it creates it with dummy data. It then checks if the recent values contain the same user (SPID) that is running now and if the last time it was triggered was within 20 seconds.
If these are true then it will PRINT 'Do Nothing' and drop the table, otherwise it will do your trigger statement.
At the end of your trigger statement it inserts into the table the SPID and current datetime.
This temp table should last as long as the SPID connection, if you want it to last longer make it a ##temp or a real table.
IF OBJECT_ID('tempdb..#temp') IS NULL
begin
Create table #temp(SPID int, dt datetime)
insert into #temp values (0, '2000-01-01')
end
If ##SPID = (select top 1 SPID from #temp order by dt desc)
and Convert(datetime,Convert(varchar(19),GETDATE(),121)) between
Convert(datetime,Convert(varchar(19),(Select top 1 dt from #temp order by dt desc),121)) and
Convert(datetime,Convert(varchar(19),DateAdd(second, 20, (select top 1 dt from #temp order by dt desc)),121))
begin
PRINT 'Do Nothing'
Drop table #temp
end
else
begin
--trigger statement
Insert into #temp values (##SPID, GETDATE())
end

Deleted Virtual table in SQL Server is empty ON Delete trigger

I am trying to invoke an ON Delete trigger event, but when I try to select row from the Deleted table, it is empty.
Is there any other way to get Id of row on which delete event has fired?
Code:
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
ALTER TRIGGER [audit]
ON [dbo].[S_PARTY]
FOR DELETE
AS
-- Insert statements for trigger here
DECLARE #id nvarchar(50)
SET #id = (Select ROW_ID from deleted )
BEGIN
-- Insert statements for trigger here
INSERT INTO [dbo].[S_AMF_AUDIT_ITEM] (ROW_ID)
VALUES (#id);
END
When trigger fires on this, I am getting error as S_AMF_AUDIT_ITEM doesn't allow null values. So can you please help me this to get Id of table on which delete command executes?
Your trigger is broken.
It doesn't take into account that the DELETE statement might affect zero or more than one rows.
The issue with NULL could occur for the statement DELETE FROM [dbo].[S_PARTY] WHERE 1 = 0.
A fixed version would be
ALTER TRIGGER [audit]
ON [dbo].[S_PARTY]
FOR DELETE
AS
BEGIN
INSERT INTO [dbo].[S_AMF_AUDIT_ITEM]
(ROW_ID)
SELECT ROW_ID
FROM deleted;
END
A trigger can fire for 0..N deleted rows. For example:
delete YourTable
where 1=2
Would run a for delete trigger on YourTable. So a trigger has to be able to deal with zero or multiple rows. Consider rewriting your trigger like:
ALTER TRIGGER [audit] ON [dbo].[S_PARTY] FOR DELETE
AS
INSERT dbo.S_AMF_AUDIT_ITEM
(ROW_ID)
SELECT ROW_ID
FROM deleted
That will work for any number of inserted rows.

trigger after insertion method

I am trying to built trigger in which when user delete a row after deleted user will able to view the row which he deleted.
i have tried my coading is follows
please help.
create trigger insertion
before insert on client
for each row
as
select * from client
Try this:
create trigger deltrig
on client
for delete
as
select deleted
delete from [<YourTable>] output deleted.*
/* where ... */
isnt something like this what you want?
create table #deleted(nr int)
create table #teste_d(nr int)
insert into #teste_d
values(1),(2),(3)
delete from #teste_d
OUTPUT deleted.nr INTO #deleted
where nr = 2
select * from #deleted
drop table #deleted
drop table #teste_d
the resultset would be what was deleted
or if you really want to use trigger
should be instead delete or update
you should do something like
insert into ##Data_deleted (col1,col2,...)
select col1,col2,... from deleted

Is there a way to make a field only editable by a trigger?

In Sql Server 2008 is there a way to set a field that it can only be changed using a Trigger?
Example:
When you create a record it is set to NULL and then updated by a trigger to e.g 1.
It should not be able to be set to anything other than NULL by the user.
And then when it is updated the trigger will set the value to 2.
create table tmp (a int primary key, b int)
GO
create trigger tr_insupd_tmp on tmp
instead of insert, update
as
if not exists(select * from deleted)
-- Process Insert
insert into tmp
select a, 1
from inserted
else
-- Process Update
update tmp
set b = 2
from tmp t
inner join inserted i on t.a = i.a
GO
Have you considered using using computed columns. If you want data in this column to be only governed by database logic then computed columns are probably way to go.