What is the best SQL query you would write to solve this problem?

The best query depends on the specific problem you’re trying to solve, but there are common patterns that make a query efficient and maintainable. First, avoid SELECT *; list only the columns you need. Use proper indexes on join and filter columns to reduce full table scans. If you need to aggregate data, use GROUP BY with appropriate indexes and consider using window functions for running totals or rankings. For joins, prefer INNER JOINs when you only need matching rows, and use LEFT JOIN only when you need all rows from the left table. Use EXISTS or IN for subqueries when you only need to test existence, as they can be faster than a JOIN. Leverage CTEs (WITH clauses) to break complex logic into readable steps. Always run EXPLAIN to inspect the query plan and look for full scans or expensive sorts. Finally, parameterize your queries to prevent SQL injection and improve caching. By following these practices, you’ll write a query that is both fast and easy to understand.