Compare SQL counts, windows, and NULL semantics

Three tables are provided. users(id INT, country VARCHAR(2), created_at DATE) holds one row per registered user. orders(order_id INT, user_id INT, amount DECIMAL(10,2), created_at DATE) records purchases, and the amount column is allowed to be NULL. events(user_id INT, event_name VARCHAR(50), event_time TIMESTAMP) records user activity. A user may have no orders at all, no events at all, or many of each. Answer all four parts below and give the exact SQL each time. (a) Write…