Объединение перекрывающихся временных интервалов на основе иерархии в SQL

Это проблема «объединения» островов. Одно из решений состоит в том, чтобы найти, где начинаются острова, и вычислить кумулятивную сумму начал. Определить начало можно, увидев, где нет перекрытий:

select id, priority, min(start_time), max(stop_time)
from (select t.*,
             countif (coalesce(prev_stop_time, stop_time) < stop_time) over (partition by id, priority order by start_time) as grp
      from (select t.*,
                   max(stop_time) over (partition by id, priority order by start_time rows between unbounded preceding and 1 preceding) as prev_stop_time
            from t
           ) t
      ) t
group by id, priority, grp;

Ниже приведен стандартный SQL BigQuery.

#standardSQL
WITH check_times AS (
  SELECT id, start_time AS time FROM `project.dataset.table` UNION DISTINCT
  SELECT id, stop_time AS time FROM `project.dataset.table` 
), distinct_intervals AS (
  SELECT id, time AS start_time, LEAD(time) OVER(PARTITION BY id ORDER BY time) stop_time
  FROM check_times
), deduped_intervals AS (
  SELECT a.id, a.start_time, a.stop_time, MIN(priority) priority
  FROM distinct_intervals a
  JOIN `project.dataset.table` b
  ON a.id = b.id 
  AND a.start_time BETWEEN b.start_time AND b.stop_time 
  AND a.stop_time BETWEEN b.start_time AND b.stop_time
  GROUP BY a.id, a.start_time, a.stop_time
), combined_intervals AS (
  SELECT id, MIN(start_time) start_time, MAX(stop_time) stop_time, ANY_VALUE(priority) priority 
  FROM (
    SELECT id, start_time, stop_time, priority, COUNTIF(flag) OVER(PARTITION BY id ORDER BY start_time) grp
    FROM (
      SELECT id, start_time, stop_time, priority, 
        start_time != IFNULL(LAG(stop_time) OVER(PARTITION BY id ORDER BY start_time), start_time) OR
        priority != IFNULL(LAG(priority) OVER(PARTITION BY id ORDER BY start_time), -1) flag
      FROM deduped_intervals
    )
  )
  GROUP BY id, grp
)
SELECT *
FROM combined_intervals
-- ORDER BY id, start_time

Если обратиться к выборочным данным из вашего вопроса - результат

Can you also share a solution where we merge intervals based on just id and no priority column

Я просто немного изменил запрос выше, чтобы игнорировать приоритет

#standardSQL
WITH check_times AS (
  SELECT id, start_time AS TIME FROM `project.dataset.table` UNION DISTINCT
  SELECT id, stop_time AS TIME FROM `project.dataset.table` 
), distinct_intervals AS (
  SELECT id, TIME AS start_time, LEAD(TIME) OVER(PARTITION BY id ORDER BY TIME) stop_time
  FROM check_times
), deduped_intervals AS (
  SELECT a.id, a.start_time, a.stop_time 
  FROM distinct_intervals a
  JOIN `project.dataset.table` b
  ON a.id = b.id 
  AND a.start_time BETWEEN b.start_time AND b.stop_time 
  AND a.stop_time BETWEEN b.start_time AND b.stop_time
  GROUP BY a.id, a.start_time, a.stop_time
), combined_intervals AS (
  SELECT id, MIN(start_time) start_time, MAX(stop_time) stop_time 
  FROM (
    SELECT id, start_time, stop_time, COUNTIF(flag) OVER(PARTITION BY id ORDER BY start_time) grp
    FROM (
      SELECT id, start_time, stop_time, 
        start_time != IFNULL(LAG(stop_time) OVER(PARTITION BY id ORDER BY start_time), start_time) flag
      FROM deduped_intervals
    )
  )
  GROUP BY id, grp
)
SELECT *
FROM combined_intervals
-- ORDER BY id, start_time   

с результатом

Row id  start_time  stop_time    
1   1   0           36   
2   1   41          47