kindly eradicate the application in the below content …

Triggers execute invisible to client-application application. They are not visible or can be traced in debugging code.

Dont mistake me sir
Munirajan.T

Just wanted to know about logging data modification.

I have seen to ways of tracking data change(DML).
1. Using Triggers
2. Keeping columns in same table for Added Date, Added By, Modified Date, Modified By.

Using approach(1), I can write trigger for Insert/Delete/Update on each table to log changes and hence can apply Foreign key relationship and other constraints like Unique key constraints on all the tables as per requirement.

But I didn’t understand how it is possible to apply various constrains using approach(2).
Since I have to make composite unique key and have to consider many more columns.

Is there any design issues in database tables. What is the suggested way for approach(2) to log data.

Which approach is better.

Also I have come to know from some of my collegues that Triggers do no fires on bulk insert queries is it true.

How can we replace a trigger by a stored procedure?

A trigger fires on UPDATE / INSERT or DELETE statement, how can we execute the stored procedure after an insert?

Thank you.

I still think there is wisdom in manually processing table links; especially if you are pruning dupes from the parent table, and don’t want to loose referential integrity with the child tables.

Thanks for the heads up – it sounds like people are using Triggers for things which they probably ought not to… for example cascading foreign key relationships.

I work in an environment where we do lots of bulk imports into clusters of child/parent tables, and if we had triggers going off each time we did anything we would have 1) a very slow environment, and 2) many many erroneous table links.

On the other hand – we also rely extensively on non-clustered indexes in order to make our reporting work in a realistic amount of time.

Is it appropriate to use a trigger to disable all table indexes before committing an UPDATE or INSERT statement, and then to rebuild the indexes AFTER the statement processes?

Thanks

Forrest

I totally agree with you on this.
To add to your thoughts, triggers are misused most of the times thereby affecting db performance. Also, all app logic should be part of the application process flow to keep things simple and visible like you said, which makes debugging easier as well.
I have trouble explaining this concept so some people.

Thanks for putting it in writing!

exp:

alter trigger trg1 on emp1 instead of insert
as
declare @empid int;
select @empid=isnumeric(empid) from inserted;
if(@empid=1)
print(‘numeric’);

else
print(‘not numeric’);

Rajneesh Hajela Gwalior (M.P.)

are U understand me sir?

These two are related to DML triggers.

After triggers are executed after executing the DML events i.e.,the trigger adn the events both are executed.These triggers can be executed only on tables.

Instead of triggers are executed instead of executing the DML events i.e., the trigger is executed without executing the DML event. These triggers can be executed on tables and views.

As the name imply the code of AFTER trigger executes after completing the trigger firing statement while code of INSTEAD of tigger executes instead of firing statement.
AFTER triger is used mostly for implementing business logic and auditing while INSTEAD of trigger is used on updatable views.

Regards,
Pinal Dave

what is the difference between after triggers and insted of triggers. and also in which situation we use triggers…plz tel me

Trigger is very powerful TSQL Command and should be used very carefully.

You cant implement Parent-Child relation with foreign key constraint, if you have your parent table in one database and your child table in other database. In this case, you can use triggers to implement foreign key relation ship.

You cant have a check constraint on a table, if you want to check a value that refers to two other tables. You can implement the same with Triggers. (You can also use a combination of Check Constraint and a function to implement the same)

You can actually start a Job inside a Trigger. If any event occurs, and you want to set a response to that event, you can set it through a trigger.

There are many more advantages of Triggers.

Starting from SQL Server 2005, We also DDL Triggers, there are NO if and No Buts to not use them… they are very very helpful… just take a look or google (DDL Triggers in SQL Server 2005) on web to know more about them.

~ IM.

CREATE TRIGGER trig_personals
ON tbl_personal
FOR UPDATE
AS
DECLARE @Flag VARCHAR(100)
DECLARE @Reg numeric(9)
IF NOT UPDATE(Flag)
BEGIN
Update tbl_general set Flag=’A’ where Reg=@Reg
END

Can u help Me.
It’s very urgent
Thanks in Advance

There are two kind of Triggers in SQL Server 2005 and Higher…
1. DML – Data Manipulation Language – INSERT, UPDATE, DELETE
2. DDL – Data Definition Language – CREATE, ALTER, DROP…. many more…

In SQL Server 2000 and lower, we had only one type of trigger, DML Triggers.

Look at these links

For DML Triggers :
http://www.sql-server-performance.com/articles/dev/triggers_2000_p1.aspx

For DDL Triggers :
http://www.sql-server-performance.com/articles/audit/ddl_triggers_p1.aspx

Google on key word : DDL Triggers in SQL Server or DML Triggers in SQL Server, you will get plenty of useful links to visit.

Take time to understand the logic, rather than remembering the syntax.

~ IM.