Question

使用MS-SQL我正在寻找构建条件交叉表查询的最佳方法，我猜这是描述它的最佳方式。

在这里简化它，我有一个CLIENTS数据集（每个都有一个唯一的ID）。每个客户端都分配给一个TEAM。大多数客户只被分配到一个团队，但有些可以分配给2,3或最多5个团队。我希望我的查询结果如下所示：

Client_ID  Assigned_Team1  Assigned_Team2  Assigned_Team3  Assigned_Team4  Assigned_Team5
---------  --------------  --------------  --------------  --------------  --------------
87496      Red Team        Null            Null            Null            Null
74559      Red Team        Blue Team       White Team      Null            Null
56345      Blue Team       Green Team      Null            Null            Null
21473      Yellow Team     Blue Team       White Team      Red Team        Green Team

Answer 1

为了获得结果，您需要使用row_number()。 row_number将用于为client_id的每个团队分配一个顺序值。然后使用此序列号将结果转换为列。有几种方法可以将数据行转换为列。（注意：我猜表结构）

您可以将聚合函数与CASE表达式一起使用：

select client_id,
  max(case when seq = 1 then team end) Assigned_Team1,
  max(case when seq = 2 then team end) Assigned_Team2,
  max(case when seq = 3 then team end) Assigned_Team3,
  max(case when seq = 4 then team end) Assigned_Team4,
  max(case when seq = 5 then team end) Assigned_Team5
from 
(
  select client_id, team,
    row_number() over(partition by client_id order by team) seq
  from clients
) d
group by client_id;

见SQL Fiddle with Demo。

或者您可以使用PIVOT功能：

select client_id,
  [1] Assigned_Team1,
  [2] Assigned_Team2, 
  [3] Assigned_Team3, 
  [4] Assigned_Team4,
  [5] Assigned_Team5
from 
(
  select client_id, team,
    row_number() over(partition by client_id order by team) seq
  from clients
) d
pivot
(
  max(team)
  for seq in ([1], [2], [3], [4], [5])
) piv;

请参阅SQL Fiddle with Demo

SQL Server条件交叉表

1 个答案: