How to Use Trigger In Oracle?

A trigger in Oracle is a type of stored procedure that is automatically executed in response to certain events occurring in a database. These events can include actions such as inserting, updating, or deleting rows in a table. Triggers can be used to enforce business rules, perform data validation, or automate certain tasks.

To create a trigger in Oracle, you first need to define the trigger's name, timing (BEFORE or AFTER), event (INSERT, UPDATE, DELETE), and scope (ROW or STATEMENT). You then write the PL/SQL code that will be executed when the trigger is fired.

Triggers can be created using the CREATE TRIGGER statement in Oracle SQL. Once a trigger is created, it will automatically execute whenever the specified event occurs. Triggers can be dropped using the DROP TRIGGER statement.

It's important to be cautious when using triggers, as they can have a significant impact on database performance if not used correctly. It's also important to test triggers thoroughly to ensure they are functioning as expected and not causing any unintended consequences.

What is a trigger body in Oracle?

In Oracle, a trigger body is the main part of a trigger that contains the PL/SQL code or SQL statements that define the actions to be taken when the trigger is fired. The trigger body is executed automatically by the Oracle database when the triggering event occurs. This code can include various actions such as updating, inserting, or deleting data in a table, or enforcing business rules or data integrity constraints. The trigger body is defined using the PL/SQL programming language and is associated with a specific table, view, or schema within the database.

What is a trigger in Oracle?

In Oracle, a trigger is a stored program that is automatically executed (or fired) in response to a specific event that occurs in a database table or view. Triggers are commonly used to enforce data integrity rules, implement business logic, or audit changes to the database.

There are two main types of triggers in Oracle:

1. Row-level triggers: These triggers fire for each row that is affected by the triggering event (such as an INSERT, UPDATE, or DELETE operation).
2. Statement-level triggers: These triggers fire once for each triggering event, regardless of the number of rows affected.

Triggers can be defined to fire either before the triggering event (BEFORE trigger) or after the triggering event (AFTER trigger). Additionally, triggers can be defined to fire either once per row (FOR EACH ROW) or once per statement (FOR EACH STATEMENT).

How to handle exceptions in triggers in Oracle?

In Oracle, you can handle exceptions in triggers using the EXCEPTION block. Here is an example of how you can handle exceptions in triggers:

1. Define the EXCEPTION block within the trigger code:

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CREATE OR REPLACE TRIGGER trg_example
BEFORE INSERT ON example_table
FOR EACH ROW
BEGIN
  -- Trigger code
EXCEPTION
  WHEN <exception_name> THEN
    -- Exception handling code
END;

1. Replace with the specific exception you want to handle. Some common exceptions in Oracle triggers include NO_DATA_FOUND, TOO_MANY_ROWS, and OTHERS.
2. Write the exception handling code within the WHEN block to handle the specific exception. This can include logging the exception, raising a custom error message, or performing any necessary cleanup operations.
3. You can also use the OTHERS exception handler to catch any other exceptions that are not explicitly defined in the trigger code.

By using the EXCEPTION block in Oracle triggers, you can effectively handle exceptions and ensure the proper functioning of your trigger logic.