Structure of the ORDERITEMS table

-Based on the structure of the ORDERITEMS table,which of the following commands will make certain that the ISBN entered actually exists in the ISBN column of the BOOKS table?
A) ALTER TABLE orderitems ADD FOREIGN KEY isbn REFERENCES BOOKS TABLE (isbn);
B) ALTER TABLE orderitems MODIFY FOREIGN KEY (isbn)REFERENCES books(isbn);
C) ALTER TABLE orderitems CREATE FOREIGN KEY (isbn)REFERENCES books(isbn);
D) ALTER TABLE orderitems ADD FOREIGN KEY (isbn)REFERENCES books(isbn);

Question

​Structure of the ORDERITEMS table
 
-Based on the structure of the ORDERITEMS table,which of the following commands will make certain that the ISBN entered actually exists in the ISBN column of the BOOKS table?​
A) ALTER TABLE orderitems ADD FOREIGN KEY isbn REFERENCES BOOKS TABLE (isbn); 
B) ALTER TABLE orderitems MODIFY FOREIGN KEY (isbn)REFERENCES books(isbn); 
C) ALTER TABLE orderitems CREATE FOREIGN KEY (isbn)REFERENCES books(isbn); 
D) ​ALTER TABLE orderitems ADD FOREIGN KEY (isbn)REFERENCES books(isbn);

Quizplus · Accepted Answer

The correct syntax for adding a foreign key to a table is "ADD FOREIGN KEY", and the correct way to reference the column in the parent table is "REFERENCES books(isbn)" (not "REFERENCES BOOKS TABLE (isbn)"). Therefore, option D is the correct command to add the foreign key constraint to the ORDERITEMS table.

​Structure of the ORDERITEMS Table

Structure of the ORDERITEMS Table