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CODE WORKSPACE
Return customer_id and country for customers with at least one shipped order.
Result columns · in this order
customer_id | Stable customer identifier. |
country | Customer country. Can be NULL when unknown. |
How to approach it
Use WHERE EXISTS against orders filtered to shipped.
Sample input
| customer_id | country |
|---|---|
| 1 | US |
| 2 | null |
| 3 | GB |
| 4 | IN |
| 6 | GB |
5 rows — all rows shown.
| order_id | buyer_id | status |
|---|---|---|
| 1004 | 1 | shipped |
| 1008 | 4 | shipped |
| 1012 | 3 | shipped |
3 rows — all rows shown.
Expected output
| customer_id | country |
|---|---|
| 1 | US |
| 3 | GB |
| 4 | IN |
3 rows — all rows shown.
Constraints
Use EXISTS correlated on customer_id. Order by customer_id.
Expected skills
Correlated subqueries and semi-join reasoning.
Submit for review to find out what your query gets right, what it gets wrong, and how it compares with the best working query for this exercise.
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