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A commerce analytics team stores every purchase event in a single order ledger and wants to identify products with stable demand across adjacent years.
Table: Orders
Business rule: A product is considered year-over-year stable if there exists at least one calendar year y where:
Important interpretation:
Task: Return one column product_id containing all products that satisfy the rule.
Supported submission environments:
Orders:
| order_id | product_id | quantity | purchase_date |
|----------|------------|----------|---------------|
| 1 | 1 | 7 | 2020-03-16 |
| 2 | 1 | 4 | 2020-12-02 |
| 3 | 1 | 7 | 2020-05-10 |
| 4 | 1 | 6 | 2021-12-23 |
| 5 | 1 | 5 | 2021-05-21 |
| 6 | 1 | 6 | 2021-10-11 |
| 7 | 2 | 6 | 2022-10-11 |[
{"product_id":1}
]Explanation
Product 1 has three orders in 2020 and three in 2021, so it qualifies. Product 2 has activity in only one year.
Orders:
| order_id | product_id | quantity | purchase_date |
|----------|------------|----------|---------------|
| 10 | 100 | 2 | 2019-01-02 |
| 11 | 100 | 5 | 2019-02-18 |
| 12 | 100 | 3 | 2019-07-20 |
| 13 | 100 | 4 | 2020-03-11 |
| 14 | 100 | 9 | 2020-11-30 |
| 15 | 101 | 1 | 2021-01-03 |
| 16 | 101 | 2 | 2021-05-09 |
| 17 | 101 | 3 | 2021-10-15 |
| 18 | 101 | 1 | 2022-02-27 |
| 19 | 101 | 2 | 2022-06-19 |
| 20 | 101 | 5 | 2022-09-01 |
| 21 | 102 | 8 | 2020-04-04 |
| 22 | 102 | 8 | 2020-08-08 |
| 23 | 102 | 8 | 2022-08-08 |
| 24 | 102 | 8 | 2022-09-09 |
| 25 | 102 | 8 | 2022-10-10 |[
{"product_id":101}
]Explanation
Product 101 qualifies via years 2021 and 2022. Product 100 misses 2020 because it has only two orders there, and product 102 has no adjacent qualifying years.
Orders:
| order_id | product_id | quantity | purchase_date |
|----------|------------|----------|---------------|
| 31 | 200 | 10000 | 2023-01-05 |
| 32 | 200 | 10000 | 2023-04-12 |
| 33 | 200 | 10000 | 2024-02-02 |
| 34 | 200 | 10000 | 2024-12-20 |
| 35 | 201 | 1 | 2024-01-01 |
| 36 | 201 | 1 | 2024-06-01 |
| 37 | 201 | 1 | 2024-11-01 |
| 38 | 201 | 1 | 2025-01-10 |
| 39 | 201 | 1 | 2025-05-10 |
| 40 | 201 | 1 | 2025-09-10 |[
{"product_id":201}
]Explanation
Qualification depends on order count, not quantity totals. Product 200 has large quantities but only two orders per year, so it does not qualify.
Constraints