Mega Code Archive

Use an instead-of trigger

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> 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> INSERT INTO session(department, course, description, max_lecturer, current_lecturer, num_credits, room_id) 2 VALUES ('HIS', 101, 'History 101', 30, 11, 4, 20000); 1 row created. 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); 1 row created. SQL> SQL> SQL> CREATE OR REPLACE VIEW session_place AS 2 SELECT department, course, building, room_number 3 FROM place, session 4 WHERE place.room_id = session.room_id; View created. SQL> SQL> SELECT * FROM session_place; DEP COURSE BUILDING ROOM_NUMBER --- ---------- --------------- ----------- HIS 301 Building 6 160 CS 101 Building 7 201 ECN 203 Building 6 101 CS 102 Building 6 150 MUS 410 Building 6 170 ECN 101 Music Building 200 NUT 307 Building 7 300 7 rows selected. SQL> SQL> CREATE TRIGGER sessionRoomsInsert 2 INSTEAD OF INSERT ON session_place 3 DECLARE 4 v_roomID place.room_id%TYPE; 5 BEGIN 6 SELECT room_id 7 INTO v_roomID 8 FROM place 9 WHERE building = :new.building 10 AND room_number = :new.room_number; 11 12 UPDATE session 13 SET room_id = v_roomID 14 WHERE department = :new.department 15 AND course = :new.course; 16 END sessionRoomsInsert; 17 / Trigger created. SQL> SQL> INSERT INTO session_place (department, course, building, room_number) 2 VALUES ('MUS', 100, 'Music Building', 200); 1 row created. SQL> SQL> SELECT * FROM session_place; DEP COURSE BUILDING ROOM_NUMBER --- ---------- --------------- ----------- HIS 301 Building 6 160 CS 101 Building 7 201 ECN 203 Building 6 101 CS 102 Building 6 150 MUS 410 Building 6 170 ECN 101 Music Building 200 NUT 307 Building 7 300 MUS 100 Music Building 200 8 rows selected. SQL> SQL> drop view session_place; View dropped. SQL> drop table session; Table dropped. SQL> drop table place; Table dropped. SQL>