在SQL Server中连接从表的两行中获取单行

Question

我需要使用连接或通过其他方式从表中的两行中取出单行。我有三个表Account，Account_Perm和User。帐户表具有一个名为AccountNum的字段，Account_Perm具有AccountNum，TeamRole和UserName的字段，用户表具有用户名。示例数据如下。

• 帐户==> AccountNum = 1234，5678
• Account_Perm ==> AccountNum = 1234，TeamRole = TeamA; AccountNum = 1234，TeamRole = TeamB
• User ==> TeamRole = TeamA，UserName = John Smith; TeamRole = TeamB，UserName =“凯西布朗”。

我需要使用这些表和我的结果集与列（AccountNum，TeamRole，TeamRole）应该如下。

1234, John Smith, Casey Brown 

通过使用加入，我能得到两行，1234，约翰·史密斯和1234，凯西·布朗。不过，我需要AccountNum，TeamA的用户名和TeamB的用户名单独记录。

有人可以帮忙吗？

查询：

SELECT 
    A.AccountNum, 
    A.TeamRole, 
    U.Name 
FROM 
    Account A, 
    Account_Perm AA, 
    User U 
WHERE 
    A.AccountNum = AA.AccountNum 
    AND AA.TeamRole IN ('TeamA', 'TeamB') 
    AND AA.UserName = U.Name; 

Answer 1

declare @Account table(AccountNum int); 
insert into @Account values (1234), (5678); 

declare @Account_Perm table (AccountNum int, TeamRole varchar(100)) 
insert into @Account_Perm values(1234, 'TeamA'), (1234, 'TeamB'); 

declare @User table (TeamRole varchar(100), UserName varchar(100)); 
insert into @User values ('TeamA', 'John Smith'), ('TeamB','Casey Brown'); 

--AccountNum, TeamRole, TeamRole) should be as below. 
--1234, John Smith, Casey Brown 
with cte AS 
(
SELECT 
    A.AccountNum, 
    AA.TeamRole, 
    U.UserName 
FROM 
    @Account A join @Account_Perm AA 
     on A.AccountNum = AA.AccountNum 
    join @User U 
     on AA.TeamRole = U.TeamRole 
WHERE AA.TeamRole IN ('TeamA', 'TeamB') 
) 

select * 
from cte pivot(max(UserName) for TeamRole in ([TeamA], [TeamB]))p