3060. User Activities within Time Bounds

SQL

WITH
  SessionDifferences AS (
    SELECT
      user_id,
      session_start,
      LAG(session_end) OVER(
        PARTITION BY user_id, session_type
        ORDER BY session_end
      ) AS prev_session_end
    FROM Sessions
  )
SELECT DISTINCT user_id
FROM SessionDifferences
WHERE TIMESTAMPDIFF(HOUR, prev_session_end, session_start) <= 12
ORDER BY 1;