枢轴并获得排名答案

【问题标题】：Pivot and also get ranking枢轴并获得排名
【发布时间】：2020-06-20 21:41:16
【问题描述】：

我正在尝试编写一个 SQL，它可以 pivot 并且还可以在一行中获得它的 ranking 顺序。不知道怎么做。

例子：

旋转area 还可以获得cost 的排名（最贵的顺序）

table name: aaa

entity_id | entity_type | datetime   | area | cost
----------+-------------+------+-----+------+-----
123       | ITEM        | 2020-01-01 | US   | 8
123       | ITEM        | 2020-01-01 | AP   | 7
123       | ITEM        | 2020-01-01 | EU   | 6
123       | ITEM        | 2020-01-02 | US   | 1
123       | ITEM        | 2020-01-02 | AP   | 2
123       | ITEM        | 2020-01-02 | EU   | 3
888       | BOX         | 2020-01-01 | US   | 8
888       | BOX         | 2020-01-01 | AP   | 7
888       | BOX         | 2020-01-01 | EU   | 6
888       | BOX         | 2020-01-02 | US   | 1
888       | BOX         | 2020-01-02 | AP   | 2
888       | BOX         | 2020-01-02 | EU   | 3

我想要的是：

entity_id | entity_type | datetime   | US | AP | EU | US_rank | AP_rank | EU_rank
----------+-------------+------------+----+----+----+---------+---------+---------
123       | ITEM        | 2020-01-01 | 8  | 7  | 6  | 1       | 2       | 3
123       | ITEM        | 2020-01-02 | 8  | 7  | 6  | 3       | 2       | 1
888       | BOX         | 2020-01-01 | 8  | 7  | 6  | 1       | 2       | 3
888       | BOX         | 2020-01-02 | 8  | 7  | 6  | 3       | 2       | 1

目前，我只知道如何旋转。不知道如何获得“排名”部分

SELECT  
  p.entity_id, p.entity_type, p.[datetime], p.[US], p.[AP], p.[EU]
FROM
  aaa as a
PIVOT
(
  MAX(cost)
  FOR area IN ([US], [AP], [EU])
) p

(which returns)

entity_id | entity_type | datetime   | US | AP | EU 
----------+-------------+------------+----+----+----
123       | ITEM        | 2020-01-01 | 8  | 7  | 6  
123       | ITEM        | 2020-01-02 | 8  | 7  | 6  
888       | BOX         | 2020-01-01 | 8  | 7  | 6  
888       | BOX         | 2020-01-02 | 8  | 7  | 6

我假设我需要在旋转之前将其添加到某处，但不知道在那之后该怎么做

ranking = ROW_NUMBER() OVER(PARTITION BY entity_id, entity_type, [datetime] ORDER BY cost DESC)

（我不介意使用RANK 或ROW_NUMBER 解决这个问题）

【问题讨论】：

标签： sql sql-server pivot row-number ranking-functions

【解决方案1】：

使用条件聚合：

select entity_id, entity_type, datetime,
       max(case when area = 'US' then cost end) as us,
       max(case when area = 'AP' then cost end) as ap,
       max(case when area = 'EU' then cost end) as eu,
       max(case when area = 'US' then rnk end) as us_rank,
       max(case when area = 'AP' then rnk end) as ap_rank,
       max(case when area = 'EU' then rnk end) as eu_rank
from (select s.*,
             rank() over (partition by entity_id, entity_type, datetime 
                          order by cost desc
                         ) as rnk
      from aaa a
     ) a
group by entity_id, entity_type, datetime

【讨论】：