Question

我有以下数据集：

 player | score |        day   
--------+-------+------------
   John |     3 | 02-01-2014
   John |     5 | 02-02-2014
   John |     7 | 02-03-2014
   John |     9 | 02-04-2014
   John |    11 | 02-05-2014
   John |    13 | 02-06-2014
   Mark |     2 | 02-01-2014
   Mark |     4 | 02-02-2014
   Mark |     6 | 02-03-2014
   Mark |     8 | 02-04-2014
   Mark |    10 | 02-05-2014
   Mark |    12 | 02-06-2014

给出两个时间范围：

02-01-2014..02-03-2014
02-04-2014..02-06-2014

我需要在给定的时间范围内获得每位玩家的平均分数。我试图实现的最终结果是：

 player | period_1_score | period_2_score
--------+----------------+----------------
   John |              5 |             11
   Mark |              4 |             10

我想出的原始算法是：

使用两个值执行SELECT，这两个值是通过将每个时间段的分数分组为两个而得出的
在第一个SELECT上，执行另一个，按玩家名称对该组进行分组。

我坚持第1步：运行以下查询：

SELECT
  player,
  AVG(score) OVER (PARTITION BY day BETWEEN '02-01-2014' AND '02-03-2014') AS period_1,
  AVG(score) OVER (PARTITION BY day BETWEEN '02-04-2014' AND '02-06-2014') AS period_2;

获取错误的结果（请注意period1和period2平均得分如何相同：

 player | period_1_score | period_2_score
--------+----------------+----------------
   John |              5 |              5
   John |              5 |              5
   John |              5 |              5
   John |              5 |              5
   John |              5 |              5
   John |              5 |              5
   Mark |              4 |              4
   Mark |              4 |              4
   Mark |              4 |              4
   Mark |              4 |              4
   Mark |              4 |              4
   Mark |              4 |              4

我想我并不完全理解窗口功能是如何工作的......我有两个问题：

我的查询有什么问题？
我该怎么做？

Answer 1

您不需要窗口功能。尝试：

select 
player
,avg(case when day BETWEEN '02-01-2014' AND '02-03-2014' then score else null end) as period_1_score
,avg(case when day BETWEEN '02-04-2014' AND '02-06-2014' then score else null end) as period_1_score
from <your data>
group by player

奇怪的窗口函数行为

1 个答案: