Window Functions Rolling Comparison

Write a SQL query using window functions to compute a 7-day rolling average and compare it to the prior week for each user.

Assume user_daily_activity contains one row per user per calendar day. Return only dates where a prior-week comparison is available.

Output

1. One row per user and activity date
2. Columns: user_id, activity_date, rolling_7_day_avg, prior_week_rolling_avg, and difference_from_prior_week
3. Include the current rolling average minus the prior-week rolling average as the difference
4. Order by user_id, then activity_date