Managing Ambiguity, Assumptions, and Data Gaps Questions

WITH params AS (
  SELECT
    now() AT TIME ZONE 'UTC' AS today_utc,
    (now() AT TIME ZONE 'UTC') - interval '30 days' AS recent_cut,
    (now() AT TIME ZONE 'UTC') - interval '90 days' AS hist_cut
),
hist AS (
  SELECT user_id, count(*) AS hist_events, max(occurred_at) AS last_hist_event
  FROM events, params
  WHERE occurred_at >= params.hist_cut
    AND occurred_at < params.recent_cut  -- 90..31 days ago
  GROUP BY user_id
),
recent AS (
  SELECT user_id, count(*) AS recent_events, max(occurred_at) AS last_event
  FROM events, params
  WHERE occurred_at >= params.recent_cut  -- last 30 days
  GROUP BY user_id
)
SELECT
  h.user_id,
  h.hist_events,
  h.last_hist_event,
  COALESCE(r.recent_events, 0) AS recent_events,
  r.last_event
FROM hist h
LEFT JOIN recent r ON h.user_id = r.user_id
WHERE COALESCE(r.recent_events, 0) = 0;