SQL interview question: Total Revenue per Customer
Customer Lifetime Value
The finance team needs to calculate total revenue generated by each customer.
Sum all order totals (total_amount) for each customer to find their lifetime value.
Return customer_id, customer_name, and lifetime_value. Only include customers who have placed at least one order.
Skills: SUM aggregation with GROUP BY and JOIN
Tables
orders 15 rows
- order_id integer PK
- customer_id integer → customers
- order_date text
- total_amount real
- status text
| order_id | customer_id | order_date | total_amount | status |
|---|---|---|---|---|
| 1 | 101 | 2024-01-20 | 249.99 | delivered |
| 2 | 101 | 2024-03-15 | 1999.99 | delivered |
| 4 | 101 | 2024-09-05 | 79.99 | delivered |
customers 12 rows
- customer_id integer PK
- name text
- email text
- city text
- signup_date text
| customer_id | name | city | signup_date | |
|---|---|---|---|---|
| 101 | Alice Mitchell | [email protected] | San Francisco | 2024-01-15 |
| 102 | Bob Chen | [email protected] | New York | 2024-02-20 |
| 103 | Carol Davis | [email protected] | Los Angeles | 2024-03-10 |