LEFT JOIN vs RIGHT JOIN decision in SQL - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all customers and their orders, even if they have no orders.

SQL

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

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

AINNER JOIN

BLEFT JOIN

CRIGHT JOIN

DFULL JOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using INNER JOIN will exclude customers without orders.

Using RIGHT JOIN will keep all orders, not all customers.

LEFT JOIN returns all rows from the left table (customers) and matching rows from the right table (orders). If no match, NULLs appear.

2fill in blank

medium

Complete the code to select all orders and their customers, even if some orders have no customer info.

SQL

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

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

ARIGHT JOIN

BINNER JOIN

CLEFT JOIN

DFULL JOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using INNER JOIN excludes orders without customers.

Using RIGHT JOIN keeps all customers, not all orders.

LEFT JOIN returns all rows from the left table (orders) and matching rows from the right table (customers). If no match, NULLs appear.

3fill in blank

hard

Fix the error in the join to get all employees and their departments, even if some employees have no department.

SQL

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

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

ARIGHT JOIN

BINNER JOIN

CCROSS JOIN

DLEFT JOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using INNER JOIN excludes employees without departments.

RIGHT JOIN keeps all departments, not employees.

LEFT JOIN keeps all employees even if they don't belong to a department. INNER JOIN excludes employees without departments.

4fill in blank

hard

Fill both blanks to select all products and their suppliers, even if some products have no supplier info.

SQL

SELECT products.name, suppliers.name FROM products [1] suppliers ON products.supplier_id [2] suppliers.id;

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

ALEFT JOIN

B=

C!=

DRIGHT JOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' in ON condition causes wrong matches.

RIGHT JOIN keeps all suppliers, not products.

LEFT JOIN keeps all products. The ON condition uses '=' to match supplier IDs.

5fill in blank

hard

Fill all three blanks to select all orders and their shipping info, even if some orders have no shipping data.

SQL

SELECT orders.id, shipping.status, shipping.date FROM orders [1] shipping ON orders.ship_id [2] shipping.id AND shipping.status [3] 'delivered';

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

ALEFT JOIN

B=

C!=

DRIGHT JOIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using RIGHT JOIN keeps all shipping info, not orders.

Using WHERE for the status filter (instead of ON) would exclude orders without shipping.

LEFT JOIN keeps all orders. ON uses '=' to match ship_id and != to only include non-delivered shipping, with NULLs otherwise.