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: ... |
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