Athena SQL - 使用外列的自联接子查询

Question

所以我在 S3 存储桶中对数据进行了编目，它与此处的数据非常相似：

+-----+-----------+---------+-----------------------+
| id  | title     | event   | time                  |
+-----+-----------+---------+-----------------------+
|1    | book A    | BORROW  | 2018-07-01 09:00:00   |
|1    | book A    | RETURN  | 2018-08-01 09:00:00   |
|2    | book B    | BORROW  | 2018-08-01 13:00:00   |
|2    | book B    | RETURN  | 2018-10-01 17:00:00   |
|1    | book A    | BORROW  | 2018-11-01 09:00:00   |
|1    | book A    | RETURN  | 2018-12-01 09:00:00   |
+-----+-----------+---------------------------------+

我基本上希望能够在 Amazon Athena 中编写一个 SELECT 语句，该语句连续显示借用和归还时间，如下所示：

+-----+-----------+-----------------------+-----------------------+
| id  | title     | borrow_time           | return_time           |
+-----+-----------+-----------------------+-----------------------+
|1    | book A    | 2018-07-01 09:00:00   | 2018-08-01 09:00:00   |
|2    | book B    | 2018-08-01 13:00:00   | 2018-10-01 17:00:00   |
|1    | book A    | 2018-11-01 09:00:00   | 2018-12-01 09:00:00   |
+-----+-----------+-----------------------+-----------------------+

我一直在花费大量时间编写大约 5 个不同的查询（使用诸如OUTER APPLY类的东西，但 Athena 似乎对使用非常敏感，特别是考虑到它没有任何OUTER APPLY功能。这是逻辑我的最新声明：

SELECT b.id,
       b.title,
       b.time AS borrow_time,
       MIN(r.time) AS return_time
FROM (
      SELECT id,
             title,
             time
      FROM books
      WHERE event = 'BORROW'
     ) b
OUTER JOIN (
            SELECT id,
                   time
            FROM books
            WHERE event = 'RETURN'
           ) r
        ON b.id = r.id
       AND b.time < r.time
GROUP BY b.id,
         b.title,
         borrow_time
ORDER BY borrow_time;

任何解决这个问题的想法将不胜感激！

Answer 1

假设借用和返回都是成对的，您可以枚举它们，然后使用条件聚合：

select id, title,
       max(case when event = 'BORROW' then b.time end) as borrow_time,
       max(case when event = 'RETURN' then b.time end) as return_time
from (select b.*,
             row_number() over (partition by b.id, b.event order by b.time) as sequm
      from books b
     ) b
group by id, title, seqnum
order by id, title, seqnum;

Answer 2

试试 CASE WHEN 和 row_number() 函数：

with pcte as 
(
 SELECT id,
           title,event,time, row_number() over(order by id,title,event) as rn
           FROM books
)
    SELECT id,
           title,
           case when event = 'BORROW' then b.time end AS borrow_time,
           case when event = 'RETURN' then b.time end AS return_time
     FROM pcte order by id, title, rn