Foreign key linking mental model in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a foreign key linking the orders table to the customers table.

SQL

ALTER TABLE orders ADD CONSTRAINT fk_customer_id FOREIGN KEY ([1]) REFERENCES customers(id);

Drag options to blanks, or click blank then click option'

Acustomer_id

Border_id

Cid

Dcustomer_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using the primary key column id of the orders table instead of the foreign key column.

Using a column that does not exist in the orders table.

The foreign key column in the orders table that links to the customers table is customer_id. This column must match the primary key id in customers.

2fill in blank

medium

Complete the code to select all orders with customer names by joining orders and customers using the foreign key.

SQL

SELECT orders.id, customers.name FROM orders JOIN customers ON orders.[1] = customers.id;

Drag options to blanks, or click blank then click option'

Aid

Bname

Ccustomer_id

Dorder_id

Attempts:

3 left

💡 Hint

Common Mistakes

Joining on the wrong columns like orders.id = customers.id.

Using a column that does not exist in orders.

The join condition uses the foreign key customer_id in orders to match the primary key id in customers.

3fill in blank

hard

Fix the error in the foreign key constraint by completing the code correctly.

SQL

ALTER TABLE orders ADD CONSTRAINT fk_customer FOREIGN KEY ([1]) REFERENCES customers([2]);

Drag options to blanks, or click blank then click option'

Acustomer_id

Border_id

Cid

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Referencing a non-primary key column in customers.

Using the wrong column name in orders.

The foreign key column in orders is customer_id and it references the primary key id in customers.

4fill in blank

hard

Fill both blanks to create a table payments with a foreign key linking to orders.

SQL

CREATE TABLE payments (id INT PRIMARY KEY, order_id INT, FOREIGN KEY ([1]) REFERENCES orders([2]));

Drag options to blanks, or click blank then click option'

Aorder_id

Bid

Dpayment_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong column name for the foreign key.

Referencing a non-primary key column in orders.

The foreign key column in payments is order_id which references the primary key id in orders.

5fill in blank

hard

Fill all three blanks to select payment ids and customer names by joining payments, orders, and customers using foreign keys.

SQL

SELECT payments.id, customers.name FROM payments JOIN orders ON payments.[1] = orders.[2] JOIN customers ON orders.[3] = customers.id;

Drag options to blanks, or click blank then click option'

Aorder_id

Bid

Ccustomer_id

Dpayment_id

Attempts:

3 left

💡 Hint

Common Mistakes

Joining on wrong columns like payments.id or orders.customer_id incorrectly.

Mixing up foreign key and primary key columns.

The joins use the foreign key order_id in payments matching id in orders, and customer_id in orders matching id in customers.