Question

尝试找出填充此表中最后一列的最快方法，streak列存储结果值的运行（win或loss）。

 game_date  | team    | result | streak 
------------+---------+--------+--------
 2017-10-05 | ABC     | win    | 1
 2017-10-07 | ABC     | win    | 2
 2017-10-11 | ABC     | loss   | 1
 2017-10-14 | ABC     | win    | 1
 2017-10-15 | ABC     | win    | 2
 2017-10-18 | ABC     | win    | 3
 2017-10-21 | ABC     | win    | 4
 2017-10-23 | ABC     | loss   | 1
 2017-10-24 | ABC     | win    | 1
 2017-10-26 | ABC     | win    | 2
 2017-10-28 | ABC     | win    | 3
 2017-10-30 | ABC     | loss   | 1
 2017-11-02 | ABC     | win    | 1
 2017-11-04 | ABC     | loss   | 1
 2017-11-07 | ABC     | win    | 1
 2017-11-09 | ABC     | loss   | 1
 2017-11-12 | ABC     | loss   | 1
 2017-11-14 | ABC     | loss   | 2
 2017-11-16 | ABC     | loss   | 3
 2017-11-18 | ABC     | win    | 1
 2017-11-19 | ABC     | loss   | 1
 2017-11-22 | ABC     | loss   | 2
 2017-11-24 | ABC     | loss   | 3
 2017-11-25 | ABC     | win    | 1
 2017-11-28 | ABC     | win    | 2
 2017-11-30 | ABC     | win    | 3
 2017-12-01 | ABC     | win    | 4
(27 rows)

如您所见，streak应该在前一个结果为空或不同时重置为1，否则递增一个。

Answer 1

您可以使用row_numbers()的差异来识别结果值的“孤岛”，从而确定胜负的顺序。其余的只是最终申请row_number()：

select g.*,
       row_number() over (partition by seqnum - seqnum_r, result order by game_date) as streak
from (select g.*,
             row_number() over (order by game_date) as seqnum,
             row_number() over (partition by result order by game_date) as seqnum_r
      from games g
     ) g

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1 个答案: