Question

以下是我的专栏：

Employees: Username, Department //a list of every employee and their department
RecentHistory: Employee1, Employee2 //a list of the previous pairings

我需要一个SELECT查询，将所有人与不属于他们部门的其他员工配对，之前他们还没有配对，我希望每个员工在返回的表格中只显示一次。
到目前为止我的查询是：

SELECT t1.Username AS Emplyee1, t2.Username AS Employee2
FROM Employees AS t1 CROSS JOIN Employees as t2
WHERE t1.Department <> t2.Department
EXCEPT
SELECT Employee1, Employee2
FROM RecentHistory
EXCEPT
SELECT Employee2, Employee1
FROM RecentHistory

这使得每个可能尚未完成的配对显示出来但它会多次返回每个员工，我希望每个员工只在结果中出现一次。

如果它有助于此查询返回与CROSS JOIN查询相同的内容：

SELECT t1.Username, t2.Username
FROM Employees AS t1 JOIN Employees AS t2
ON (t1.Department <> t2.Department)
EXCEPT
SELECT Employee1, Employee2
FROM RecentHistory
EXCEPT
SELECT Employee2, Employee1
FROM RecentHistory

Answer 1

DECLARE @outTable AS TABLE (Employee1 nvarchar(20), Employee2 nvarchar(20))

DECLARE @users AS TABLE (RowId INT IDENTITY, Username nvarchar(20), Department nvarchar(20))
DECLARE @i int, @cnt int, @username nvarchar(20);

INSERT INTO @users
SELECT Username, Department FROM dbo.Employees 

SELECT @i = 1, @cnt = count(*) from @users

WHILE @i <= @cnt
BEGIN
    SELECT @username =  Username from @users where RowId = @i;

    INSERT INTO @outTable
    SELECT TOP 1 t1.Username AS Employee1, t2.Username AS Employee2 
    FROM Employees AS t1 CROSS JOIN Employees as t2
    WHERE t1.Department <> t2.Department 
    AND t1.Username = @username
    AND t1.Username not in (select Employee2 from @outTable UNION select Employee1 from @outTable)
    AND t2.Username not in (select Employee2 from @outTable UNION select Employee1 from @outTable)
    EXCEPT
    SELECT Employee1, Employee2
    FROM RecentHistory
    EXCEPT
    SELECT Employee2, Employee1
    FROM RecentHistory 

    SET @i = @i + 1

END

select * from @outTable

需要配对表中的每个人，但我不希望任何人使用多次

1 个答案: