To create a database trigger:
CREATE TRIGGER no_weekend_updates
BEFORE UPDATE
ON EMP
DECLARE
day_of_week NUMBER(2) := TO_NUMBER(TO_CHAR(SYSDATE,'D'));
dummy CHAR(1);
BEGIN
IF (day_of_week in (1,7)) /* Sunday,Saturday */
THEN
BEGIN
SELECT 'X'/* Check Exceptions Table */
INTO dummy
FROM WEEKEND_UPDATE_OK
WHERE USERID = USER;
EXCEPTION
WHEN NO_DATA_FOUND THEN /*Not Exception*/
RAISE_APPLICATION_ERROR(-20011,
'Try again on Monday!');
END;
END IF;
END;