Joining on primary key to foreign key in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all columns from both tables where the primary key matches the foreign key.

SQL

SELECT * FROM orders JOIN customers ON orders.customer_id = customers.[1];

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 foreign key column name instead of the primary key column name in the join condition.

Joining on columns that do not relate to each other.

The foreign key orders.customer_id matches the primary key customers.id. So, we join on customers.id.

2fill in blank

medium

Complete the code to join employees and departments on the foreign key department_id.

SQL

SELECT employees.name, departments.name FROM employees JOIN departments ON employees.[1] = departments.id;

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

Adept_id

Bid

Cname

Ddepartment_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using the primary key column name from employees instead of the foreign key.

Mixing up column names between tables.

The foreign key in employees is department_id, which matches the primary key departments.id.

3fill in blank

hard

Fix the error in the join condition to correctly join sales and products.

SQL

SELECT * FROM sales JOIN products ON sales.product_id = products.[1];

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

Aid

Bsales_id

Cprice

Dproduct_name

Attempts:

3 left

💡 Hint

Common Mistakes

Joining on non-key columns like product_name.

Using the wrong table's column in the join condition.

The foreign key sales.product_id should match the primary key products.id. Joining on other columns causes errors or wrong results.

4fill in blank

hard

Fill both blanks to join invoices and clients on the correct keys.

SQL

SELECT invoices.id, clients.name FROM invoices JOIN clients ON invoices.[1] = clients.[2];

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

Aclient_id

Binvoice_id

Cid

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the foreign key and primary key columns.

Joining on non-key columns like name.

The foreign key invoices.client_id matches the primary key clients.id. This is the correct join condition.

5fill in blank

hard

Fill all three blanks to join payments and orders and select payment amount and order date.

SQL

SELECT payments.amount, orders.[1] FROM payments JOIN orders ON payments.[2] = orders.[3];

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

Aorder_date

Border_id

Cid

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting the wrong column from orders.

Mixing up foreign key and primary key columns in the join.

The foreign key payments.order_id matches the primary key orders.id. We select orders.order_date to see when the order was made.