Oracle PL/SQL Programming: A Developer's Workbook

Expert

16-30.	If you create several triggers of the same type for the same table, in what order do the triggers fire?
16-31.	Optimize the performance of the following trigger and explain how this technique can minimize the number of times the trigger fires: CREATE OR REPLACE TRIGGER employee_ins_t1 AFTER UPDATE OR DELETE OR INSERT ON employee FOR EACH ROW BEGIN IF (UPDATING) THEN IF :old.sal <> :new.sal THEN Employee_pkg.update_emp (:new.employee_id, :new.sal); END IF; END IF; END;
16-32.	An HR system has an employee table that holds a row for each employee within the company. Each record in the table has a manager field, (mgr), that holds the ID for the employee’s manager. Write a trigger so that when a manager record is deleted, the mgr field of that manager’s employees is set to NULL. In other words, implement the following SQL statement: WHEN AN EMPLOYEE IS DELETED, UPDATE employee SET mgr = null WHERE mgr = employee id of the deleted employee
16-33.	Due to a runtime error, an AFTER LOGON trigger in your database has become invalid. As a consequence, all users receive the following error when trying to connect to the database: ORA-04098: trigger 'ON_LOGON' is invalid and failed re-validation How can you fix the problem?
16-34.	What are the possible implications of using the pseudo-column names :OLD and :NEW in the following trigger, which uses autonomous transactions? /* Filename on web page: ...