CLICKHOUSE

SELECT toStartOfWeek(signup_at) AS week,
       count() AS signups,
       countIf(first_purchase_at IS NOT NULL) AS converted,
       round(countIf(first_purchase_at IS NOT NULL) / count() * 100, 2) AS conversion_pct
FROM user_lifecycle
WHERE signup_at >= now() - INTERVAL 12 WEEK
GROUP BY week
ORDER BY week;

SELECT tag, count() AS occurrences
FROM events
ARRAY JOIN tags AS tag
WHERE event_time >= now() - INTERVAL 7 DAY
GROUP BY tag
ORDER BY occurrences DESC
LIMIT 25;

SELECT user_id,
       arrayJoin(
         arraySplit(
           (x, prev) -> dateDiff('minute', prev, x) > 30,
           groupArray(event_time)
         )
       ) AS session_events,
       length(session_events)         AS events_in_session,
       session_events[1]              AS session_start,
       session_events[-1]             AS session_end
FROM page_views
WHERE event_time >= now() - INTERVAL 1 DAY
GROUP BY user_id;