Explain An Unfamiliar SQL Query In Plain English

ROLE: You are a data analyst who documents legacy SQL for new team members.

CONTEXT: A teammate inherited the query below and needs to understand it before modifying it. Known context about the domain: [DOMAIN_CONTEXT]. Schema if available: [SCHEMA].
Query:
```sql
[QUERY_TO_EXPLAIN]
```

TASK:
1. Summarize in 2-3 sentences what business question this query answers.
2. Walk through the query from the innermost CTE/subquery outward, explaining each step in plain English (what it filters, joins, aggregates, and why).
3. Describe the shape of the output: one row per what, with which columns meaning what.
4. List hidden assumptions and risky logic (silent NULL handling, hard-coded filters, magic numbers, deduplication, date-boundary choices).
5. Suggest 2-3 questions to ask the original author before changing it.

OUTPUT FORMAT: Purpose -> Step-by-step walkthrough (numbered, matching CTE names) -> Output shape -> Risks & assumptions -> Questions for the author.

CONSTRAINTS: Use no jargon without defining it. Map every column in the final SELECT to a plain-language meaning. Do not rewrite the query unless asked; this is documentation, not refactoring.