SQL Database Concepts

Explain key database concepts you rely on when writing and optimizing SQL queries.

Use the provided customer and order tables to demonstrate these concepts in one query. Return every customer, including customers without qualifying orders, and apply the date and status criteria without excluding unmatched customers.

Output

1. One row per customer with customer_id, customer_name, completed_order_count, completed_revenue, and revenue_band
2. Include only completed orders from 2025, while retaining customers with none
3. Sort by completed_revenue descending, then customer_name ascending