Basic SQL Querying (Filtering, Aggregation, Join, Window Functions)

Prompt: Basic SQL Queries You are given two tables: users user_id (INT) country (STRING) signup_date (DATE) events event_id (INT) user_id (INT) event_time (TIMESTAMP) event_type (STRING) value (FLOAT) Write SQL (one or multiple queries) to: Count users per country. Compute DAU: distinct active users per day (DATE(event_time)). For each user, return the first event time and its event type. For each country, compute a 7-day rolling active-user count per day (inclusive), ordered by date (window functions allowed). Constraints events.user_id always exists in users.user_id. Use standard SQL (PostgreSQL or ANSI SQL acceptable). Scale users up to 1,000,000 rows events up to 100,000,000 rows