SQL查询以获取序列的首尾

Question

通过以下查询...

select aa.trip_id, aa.arrival_time, aa.departure_time, aa.stop_sequence, aa.stop_id, bb.stop_name
from  OeBB_Stop_Times aa
left join OeBB_Stops bb on aa.stop_id = bb.stop_id

我得到下表：

现在，我想要来自stop_sequence列的第一行和最后一行/值引用列trip_id，所以结果应该是：

我该怎么做？

谢谢

Answer 1

您可以执行子查询以获取最小值和最大值，并根据该数据进行联接。
像这样：

select aa.trip_id, aa.arrival_time, aa.departure_time, aa.stop_sequence, aa.stop_id, bb.stop_name
from  OeBB_Stop_Times aa
join (
   SELECT trip_id, max(stop_sequence) as max_stop, min(stop_sequence) as min_stop
   FROM OeBB_Stop_Times
   GROUP BY trip_di
) sub on aa.trip_id = sub.trip_id AND (aa.stop_sequence = sub.max_stop or aa.stop_sequence = sub.min_stop)
left join OeBB_Stops bb on aa.stop_id = bb.stop_id

Answer 2

您可以两次使用ROW_NUMBER()窗口函数来过滤出行，如下所示：

select *
from (
  select *,
    row_number() over(partition by trip_id order by arrival_time) as rn,
    row_number() over(partition by trip_id order by arrival_time desc) as rnr
  from OeBB_Stop_Times
) x
where rn = 1 or rnr = 1
order by trip_id, arrival_time

Answer 3

您可以使用row_number()：

select s.*
from (select st.trip_id, st.arrival_time, st.departure_time, 
             st.stop_sequence, st.stop_id, s.stop_name,
             row_number() over (partition by st.trip_id order by st.stop_sequence) as seqnum_asc,
             row_number() over (partition by st.trip_id order by st.stop_sequence desc) as seqnum_desc
      from OeBB_Stop_Times st left join
           OeBB_Stops s
           on st.stop_id = s.stop_id
     ) s
where 1 in (seqnum_asc, seqnum_desc);

请注意，我修复了表别名，以便它们有意义而不是任意字母。

实际上，如果保证stop_sequence从1开始，这会更简单：

select s.*
from (select st.trip_id, st.arrival_time, st.departure_time, 
             st.stop_sequence, st.stop_id, s.stop_name,
             max(stop_sequence) over (partition by st.trip_id) as max_stop_sequence
      from OeBB_Stop_Times st left join
           OeBB_Stops s
           on st.stop_id = s.stop_id
     ) s
where stop_sequence in (1, max_stop_sequence);