Join and Aggregate Claims Data

Write a SQL query to join multiple tables, aggregate claims data by region, and filter out low-value policyholders.

Treat a low-value policyholder as one whose combined policy premium is below 1,000. Include claims from qualifying policyholders, including policyholders with no claims.

Output

1. One row per region, including a null region when applicable.
2. Return region, qualifying_policyholder_count, total_claim_amount, and average_claim_amount_per_policyholder.
3. Sort by region ascending, with the null region last.