signups(user_id, signup_at) and events(user_id, event_type, event_at)

For users who signed up in September 2026, return activation_rate_pct: the percentage who performed an 'activate' event within 7 days of signing up, rounded to two decimals.

Each user counts once however many times they activated. An activation before signup, or on day 8, does not count.

Tables

events

user_id  event_type  event_at
-------  ----------  -------------------
1        activate    2026-09-02 10:00:00
1        activate    2026-09-05 10:00:00
2        activate    2026-09-10 11:00:00
3        activate    2026-09-01 10:00:00
5        activate    2026-08-21 10:00:00

signups

user_id  signup_at
-------  -------------------
1        2026-09-01 10:00:00
2        2026-09-02 10:00:00
3        2026-09-03 10:00:00
4        2026-09-04 10:00:00
5        2026-08-20 10:00:00

Expected result

activation_rate_pct
-------------------
25.00