Customer ID Gap Detector

A customer data platform receives account records from multiple systems.

Table: customers

• customer_id: unique integer identifier for each customer
• customer_name: display name for the customer

Task: Find all missing customer IDs in the integer range from 1 to the maximum customer_id currently present in the table.

Definition:

• If max(customer_id) = M, evaluate every integer in [1, M].
• Any integer in that range that is absent from customers.customer_id is considered missing.

Output requirements:

• Return exactly one column named ids.
• Sort result rows by ids in ascending order.

Notes:

• customer_id is unique.
• The maximum customer_id in any test case does not exceed 100.

Supported submission environments:

• SQL (SQLite 3.27.2)
• Pandas (Python)

customers:
| customer_id | customer_name |
|-------------|---------------|
| 1           | Alice         |
| 4           | Bob           |
| 5           | Charlie       |

[
  {"ids":2},
  {"ids":3}
]

customers:
| customer_id | customer_name |
|-------------|---------------|
| 2           | Nia           |
| 3           | Omar          |
| 5           | Pia           |
| 9           | Quin          |

[
  {"ids":1},
  {"ids":4},
  {"ids":6},
  {"ids":7},
  {"ids":8}
]

customers:
| customer_id | customer_name |
|-------------|---------------|
| 1           | Ava           |
| 2           | Ben           |
| 3           | Cara          |
| 4           | Dan           |

[]