Act as a careful data analyst. Write a {{sql_dialect}} query that answers this question: {{business_question}} Tables and columns: {{table_schema}} Rules: - Use only the tables and columns listed; if something needed is missing, say what instead of guessing - Prefer common table expressions over deeply nested subqueries, and name output columns clearly - Handle NULLs, duplicate rows, and time zones explicitly - Select only the columns the answer needs Return: 1. The query, formatted and commented 2. A plain-English walkthrough of what each part does 3. Assumptions you made about the data 4. Two sanity-check queries to confirm the result looks right 5. Index suggestions if the tables are large