Top Clients by Region SQL

A financial reporting team needs a quarterly view of its highest-spending clients by region. Write a PostgreSQL query to identify the top three clients in each non-null region based on transaction amounts from the previous calendar quarter relative to the fixed reporting date of September 15, 2026.

Output

1. Return one row per qualifying client with columns region, client_id, client_name, total_spent, and spending_rank.
2. Aggregate all qualifying transactions for each region and client. SUM ignores NULL amounts, so a client whose qualifying amounts are all NULL has a NULL total_spent.
3. Exclude transactions with a NULL region. Return at most three clients per region, ranking higher totals first and using client_id as the deterministic tie-breaker.
4. Sort by region, then spending_rank, then client_id.