wk_signups (user_id, signup_date) has one row per user; wk_activity (activity_id, user_id, active_on) one row per user and day they were active. Both columns are DATEs.
Users are grouped into signup weeks. Weeks start on Monday: cohort_week is the Monday on or before the signup date. Every signup counts toward its cohort, whether or not it was ever active.
Report day-7 retention two ways:
- •on day 7 (classic) — active on exactly
signup_date + 7 days - •day 7 or later (unbounded) — active on
signup_date + 7 days or on any later date
Columns: cohort_week (a DATE), cohort_size, day7_users, day7_plus_users, day7_pct, day7_plus_pct (the two counts as a percentage of cohort_size, rounded to 1 decimal place). Sort by cohort_week.