SQL>
SQL>
SQL> CREATE TABLE place (
2 room_id NUMBER(5) PRIMARY KEY,
3 building VARCHAR2(15),
4 room_number NUMBER(4),
5 number_seats NUMBER(4),
6 description VARCHAR2(50)
7 );
Table created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20001, 'Building 7', 201, 1000, 'Large Lecture Hall');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20002, 'Building 6', 101, 500, 'Small Lecture Hall');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20003, 'Building 6', 150, 50, 'Discussion Room A');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20004, 'Building 6', 160, 50, 'Discussion Room B');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats,description)
2 VALUES (20005, 'Building 6', 170, 50, 'Discussion Room C');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20006, 'Music Building', 100, 10, 'Music Practice Room');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20007, 'Music Building', 200, 1000, 'Concert Room');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats, description)
2 VALUES (20008, 'Building 7', 300, 75, 'Discussion Room D');
1 row created.
SQL>
SQL> INSERT INTO place (room_id, building, room_number, number_seats,description)
2 VALUES (20009, 'Building 7', 310, 50, 'Discussion Room E');
1 row created.
SQL> CREATE TABLE session (
2 department CHAR(3),
3 course NUMBER(3),
4 description VARCHAR2(2000),
5 max_lecturer NUMBER(3),
6 current_lecturer NUMBER(3),
7 num_credits NUMBER(1),
8 room_id NUMBER(5)
9 );
Table created.
SQL>
SQL> CREATE OR REPLACE TRIGGER CheckRoomID
2 BEFORE INSERT OR UPDATE OF room_id
3 ON session
4 FOR EACH ROW
5 DECLARE
6 v_RoomID NUMBER(5);
7 BEGIN
8 SELECT room_id
9 into v_RoomID
10 FROM place
11 where room_id = :new.room_id;
12 EXCEPTION
13 WHEN NO_DATA_FOUND THEN
14 RAISE_APPLICATION_ERROR(-20000, :new.room_id || ' is not a ' ||
15 ' valid room');
16 END CheckRoomID;
17 /
Trigger created.
SQL>
SQL>
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('HIS', 101, 'History 101', 30, 11, 4, 20000);
INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
*
ERROR at line 1:
ORA-20000: 20000 is not a valid room
ORA-06512: at "RNTSOFT.CHECKROOMID", line 10
ORA-04088: error during execution of trigger 'RNTSOFT.CHECKROOMID'
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('HIS', 301, 'History 301', 30, 0, 4, 20004);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('CS', 101, 'Computer Science 101', 50, 0, 4, 20001);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('ECN', 203, 'Economics 203', 15, 0, 3, 20002);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('CS', 102, 'Computer Science 102', 35, 3, 4, 20003);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('MUS', 410, 'Music 410', 5, 4, 3, 20005);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('ECN', 101, 'Economics 101', 50, 0, 4, 20007);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('NUT', 307, 'Nutrition 307', 20, 2, 4, 20008);
1 row created.
SQL>
SQL> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
2 VALUES ('MUS', 100, 'Music 100', 100, 0, 3, NULL);
INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id)
*
ERROR at line 1:
ORA-20000: is not a valid room
ORA-06512: at "RNTSOFT.CHECKROOMID", line 10
ORA-04088: error during execution of trigger 'RNTSOFT.CHECKROOMID'
SQL>
SQL>
SQL>
SQL> drop table session;
Table dropped.
SQL>
SQL> drop table place;
Table dropped.