3497. Analyze Subscription Conversion

Table: UserActivity +------------------+---------+ | Column Name | Type | +------------------+---------+ | user_id | int | | activity_date | date | | activity_type | varchar | | activity_duration| int | +------------------+---------+ (user_id, activity_date, activity_type) is the unique key for this table. activity_type is one of ('free_trial', 'paid', 'cancelled'). activity_duration is the numbe