a trigger code

I have table T1 and I am trying to extract some date from T1 table based on inserts, updates and deletes. The destination table T2 has three fields F1, F2, F3, so I need something like

Insert into T2 (F1, F2, F3)

Select (F1, F2,Type)

From T1

Type should be defined based on Insert, Update, or Delete. This will be my first trigger, Can anyone write this trigger for me?

If you want to determine type of trigger action from single trigger then see code below:

set nocount on
go
if object_id('tr_tbl') is not null
drop table tr_tbl
go
create table tr_tbl(i int)
go
create trigger tr_test on tr_tbl for insert, update, delete as
if exists(select * from inserted) and exists(select * from deleted)
print 'Update...' -- set @.type = 'U'
else
if exists(select * from inserted)
print 'Insert...' -- set @.type = 'I'
else
print 'Delete...' -- set @.type = 'D'

... your code
go

insert tr_tbl values(1)
update tr_tbl set i = i + 1
delete tr_tbl

go

drop table tr_tbl

go

But it might be easier writing separate triggers. And you shouldn't query the base table T1 directly since you will get all rows in the table and not just the rows affected by the DML. You need to use the inserted/deleted tables based on the trigger action.

|||

This helps a lot, thanks,

One question: since there are more than one user on the system will there be a case that insert virtual table might have more than one row?

|||Yes, you should always write your trigger code such that it handles multiple rows. This will also force you to use simple set of DMLs from trigger for the logic which is more efficient than a procedural approach. If you want to enforce only singleton operations via DML then you can do so within trigger by checking for @.@.ROWCOUNT and rolling back the transaction/ DML operation.sql