CREATE TABLE order_item 
   (order_id INTEGER, 
    item_id INTEGER,
    quantity INTEGER, 
    unit_price DOUBLE,
    FOREIGN KEY (order_id) REFERENCES sales_order (id),
    FOREIGN KEY (item_id) REFERENCES item (id),
    PRIMARY KEY (order_id, item_id));
                                                                                                  
INSERT INTO order_item VALUES (1,  1,  4, 27.00);

INSERT INTO order_item VALUES (1,  2,  2, 210.50);

INSERT INTO order_item VALUES (1,  3,  1, 569.00);

INSERT INTO order_item VALUES (2,  2,  2, 230.95);

INSERT INTO order_item VALUES (3,  1,  3, 27.00);

INSERT INTO order_item VALUES (3,  2,  1, 230.95);

INSERT INTO order_item VALUES (4,  3,  1, 569.00);

INSERT INTO order_item VALUES (5,  1,  2, 27.00);

INSERT INTO order_item VALUES (5,  3,  1, 725.00);