I created the Employee table which contains EmpNo,EName,EDesignation as its fields.Also i created the 3 Triggers namely Trigger_1,Trigger_2 and Trigger_3.All the Triggers are Statement level triggers and fired after the update done in the table.Now i want the following orders in which the triggers are going to fired when the update statement is executed.
The Order is
Trigger_3,
Trigger_1,
Trigger_2
Can anyone tell me the way to fire the trigger events in userdefined way?I m using Oracle 9i
Trigger Evaluation Order
Quote from Oracle documentation:
Although any trigger can run a
sequence of operations either in-line
or by calling procedures, using
multiple triggers of the same type
enhances database administration by
permitting the modular installation of
applications that have triggers on the
same tables.
Oracle Database executes all triggers
of the same type before executing
triggers of a different type. If you
have multiple triggers of the same
type on a single table, then Oracle
Database chooses an arbitrary order to
execute these triggers.
Each subsequent trigger sees the
changes made by the previously fired
triggers. Each trigger can see the old
and new values. The old values are the
original values, and the new values
are the current values, as set by the
most recently fired UPDATE or INSERT
trigger.
To ensure that multiple triggered
actions occur in a specific order, you
must consolidate these actions into a
single trigger (for example, by having
the trigger call a series of
procedures).
see also http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14251/adfns_triggers.htm
Have one trigger with the contents of the three.
If you cannot, for reasons for modularization, reusability..., create three stored procedures and call these one by one in the single trigger.
Upgrade to 11g and you can define trigger execution order
Related
I would like to know how to use "oracle triggers" to clone a user or copy all the roles and rights from one user to other.
The procedure should contain two parameter. One source user and other target user.
I wouldn't use a trigger for that. A trigger is a stored program unit that gets executed when one of the following operations occur:
DML statement on a table or view
DDL statement by a particular user
Database event
The list doesn't contain an event that triggers the cloning of a user. Besides, triggers don't have parameters like old or new users.
This overview explains nicely what triggers can do.
I am new to Triggers in database and ECA.
According to my understanding, Triggers are the automated procedures in PL/SQl that are fired based upon some Event and Condition which is provide by ECA.
But does ECA has its own independent significance in database, it some independent system? or How do Triggers and ECA relate to each other ?
Any help on the above topics is highly appreciated .
Triggers mechanism allows to bind custom procedures to low level DML operations like insert, update and delete. Procedures are created by language used by data base, for example: oracle uses pl/sql, sql server uses tsql and other can use others.
For example:
Developer can create trigger on delete operation on table customers that invoke procedure that create log.
You can say Trigger is fulfilling ECA concept.
Event - is DML operation on data.
Condition - defined during trigger creation.
Action - procedure defined by developer.
I have a confusion on maximum numbers of different type of triggers we can have on a single table in oracle db.
Do you encounter any problems due to any limit?
You can have triggers of these timing points:
BEFORE statement triggers
BEFORE row triggers
AFTER row triggers
AFTER statement triggers
In case you have more than one trigger at a timing point the order of execution is undetermined, thus it should be very uncommon to have many triggers for the same timing point.
Oracle documentation says:
You cannot control the order in which multiple row triggers fire.
If two or more triggers are defined with the same timing point, and the order in which they fire is important, then you can control the firing order using the FOLLOWS clause.
You can have more than one trigger at same point of time.
You can achieve that using FOLLOWS keyword while creating trigger.
Like in procedures and Functions can we pass parameters to triggers? Can A trigger can be explicitly called?
An object based trigger is raised by an event's occurence(as update,insert,select)on a specific object of the database. There is also system triggers, fired by system specific events(as shutdown,startup database, user connection etc..).
This is the main purpose of a trigger in databases, you can't raise it explicitly, if you want it to run the only way is to raise the event. Also passing parameters isn't part of trigger definition, but you can handle the event attributes,(which can be passed to the trigger body that may can contain functions or procedures).
I hope that i've responded to your question, can i know what is your need for trying to do that.?
What you can do is to create a table that will store temporarily the data that you want to access in your trigger.
1-Create a table "tmp_data" for instance.
2-Before running the event that will fire the trigger (stored procedure, insert, update...) insert into tmp_data the data that you want to use in the trigger.
3-In the trigger, to access the data you needed, you make a query on the table tmp_data.
4-After have been done with the data, you clean the table tmp_data for the next use.
Hope has been helpful!
If a trigger is already in function what will be the effect if i will replace a small part of it ,so many records are getting inserted in table A continuously in which the trigger is applied.
Trigger X is running in table A,
total records are getting insterted per minute are 1000
If i have replaced the trigger what will be the Impact of It for those service who are accesing the table.
Thanks in advance
A CREATE TRIGGER DDL should have no impact on your running DML transactions. Exclusive locks are not required on the table in order to add the trigger.
A CREATE OR REPLACE DDL is slightly different. It has to change an existing object. If the trigger is actively firing, the new trigger will try to lock the trigger object in the library cache before altering it. No impact on the table.
I generally observe that triggers execute immediately.
If you have tested your trigger, you should have no issues. If the trigger is correct, it will go into effect, and the impact shall be according to the logic that you've written in the trigger. The act of creating the trigger is not of concern, but the correctness of the trigger code is. So test it well.
Any transactions underway at the time you create the trigger will finish without firing the trigger.
Any future transactions will fire the trigger.