Write SQL for top spender and non-spenders

SQL Questions

Assume the following schema:

• users(user_id, created_at, ...)
• transactions(txn_id, user_id, amount, txn_ts)
  • amount is a positive number for a successful purchase.

Q1: Biggest spender last month

Write a SQL query to find the user(s) with the largest total spend in the previous calendar month.

Q2: Users who never spent

Write a SQL query to find users who have never made a purchase (no rows in transactions).

If you need additional assumptions (timezone, refunds, ties), state them explicitly.