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Case 39 of 50
Case 039: Spending Quartiles
customersorderspayments
The manager wants to split the customer base into four equal-sized tiers for a targeting campaign.
"Rather than exact ranks, could you just tell me which quartile each customer falls into?"
The data Alex is looking at
customers
| id | name | country | signup_date |
|---|---|---|---|
| 1 | Sam | Germany | 2026-01-02 |
| 2 | Nina | Canada | 2026-01-05 |
| 3 | David | Germany | 2026-01-10 |
| 4 | Maya | Japan | 2026-01-15 |
| 5 | Daniel | Canada | 2026-01-20 |
| … 5 more rows | |||
orders
| id | customer_id | order_date |
|---|---|---|
| 101 | 1 | 2026-01-05 |
| 102 | 2 | 2026-01-08 |
| 103 | 3 | 2026-01-12 |
| 104 | 1 | 2026-01-20 |
| 105 | 4 | 2026-02-01 |
| … 23 more rows | ||
payments
| id | order_id | amount |
|---|---|---|
| 601 | 101 | 6200 |
| 602 | 102 | 3500 |
| 603 | 103 | 3600 |
| 604 | 104 | 60000 |
| 605 | 105 | 12000 |
| … 23 more rows | ||
TASK
Help Alex answer the manager:
“Split customers into four equal-sized groups (quartiles) based on total spending, showing their total and which quartile they fall into — highest spenders in quartile 1.”
Write a query above and hit Run to see what comes back.
No hints requested yet — click "Get a hint" when you're stuck.
Alex's final query — this is for reference. Copy it into your own thinking, not into the editor above.
WITH customer_totals AS (
SELECT
customers.name,
SUM(payments.amount) AS total
FROM customers
JOIN orders ON customers.id = orders.customer_id
JOIN payments ON payments.order_id = orders.id
GROUP BY customers.name
)
SELECT
name,
total,
NTILE(4) OVER (ORDER BY total DESC) AS spending_quartile
FROM customer_totals;
What that query returns
Case Debrief
NTILE()
- NTILE(n) buckets ordered rows into n equal-sized groups — quartiles are NTILE(4), deciles are NTILE(10) (tenths instead of quarters), and any other n works the same way for any "split into tiers" question.