Triggers in Oracle

 Triggers in Oracle

A trigger is a piece of code that is automatically executed in response to a certain event, such as an insert, update, or delete operation on a table. Triggers are used to enforce business rules and maintain data integrity. Here is an example:

CREATE OR REPLACE TRIGGER emp_salary_trigger

BEFORE INSERT OR UPDATE ON employees

FOR EACH ROW

BEGIN

   IF :NEW.salary < 0 THEN

      raise_application_error(-20001, 'Salary cannot be negative');

   END IF;

END;

This creates a trigger named "emp_salary_trigger" that is executed before an insert or update operation on the "employees" table. If the new salary value is less than 0, an error is raised.