Question

我有一张员工表emp，如下所示：

emp_id    emp_name   emp_role
______________________________
1          aaaa       Supervisor
2          bbbb       Supervisor
3          cccc       helper
4          dddd       helper
5          eeee       helper
6          ffff       helper

另一个表Supervisor和辅助映射（Sup_Helper_Map）：

supervisor_id      helper_id
____________________________
1                   3
1                   4
2                   5
2                   6

如果可能，我希望在单个查询中使用以下结构中的数据，例如，。

Supervisor_id   Supervisor_name   helper_id        helper_name
_______________________________________________________________
1                 aaaa             3                 cccc
1                 aaaa             4                 dddd
2                 bbbb             5                 eeee
2                 bbbb             6                 ffff

Answer 1

你可以简单地加入Employee表2次，以获得预期的结果。

使用给定的样本数据进行演示：

DECLARE @Employee TABLE (emp_id  INT, emp_name VARCHAR (100), emp_role VARCHAR (100));

INSERT INTO @Employee (emp_id, emp_name, emp_role) VALUES
(1, 'aaaa', 'Supervisor'),
(2, 'bbbb', 'Supervisor'),
(3, 'cccc', 'helper'),
(4, 'dddd', 'helper'),
(5, 'eeee', 'helper'),
(6, 'ffff', 'helper');

DECLARE @Sup_Helper_Map TABLE (Supervisor_id  INT, Helper_id INT);

INSERT INTO @Sup_Helper_Map (Supervisor_id, Helper_id) VALUES
(1, 3),
(1, 4),
(2, 5),
(2, 6);

SELECT M1.Supervisor_id, E1.emp_name AS Supervisor_name, 
       M1.Helper_id, E2.emp_name AS Helper_name
FROM @Sup_Helper_Map M1
JOIN @Employee E1 ON E1.emp_id = M1.Supervisor_id
JOIN @Employee E2 ON E2.emp_id = M1.Helper_id

结果：

Supervisor_id   Supervisor_name Helper_id   Helper_name
--------------------------------------------------------
1               aaaa            3           cccc
1               aaaa            4           dddd
2               bbbb            5           eeee
2               bbbb            6           ffff

Answer 2

试试这个

SELECT
    s.supervisor_id,
    e.emp_name supervisor_Name,
    s.helper_id,
    h.emp_name helper_name
FROM
    emp e INNER JOIN 
    Sup_Helper_Map s ON e.emp_id = s.supervisor_id INNER JOIN 
    emp h ON s.helper_id = h.emp_id

Answer 3

SELECT        dbo.Sub_Helper_Map.supervisor_id, emp1_1.emp_name AS Supervisor_name, dbo.Sub_Helper_Map.helper_id, dbo.emp.emp_name AS helper_name
FROM            dbo.emp INNER JOIN
                         dbo.Sub_Helper_Map ON dbo.emp.emp_id = dbo.Sub_Helper_Map.helper_id INNER JOIN
                         dbo.emp AS emp1_1 ON dbo.Sub_Helper_Map.supervisor_id = emp1_1.emp_id

获得一对多关系的价值

3 个答案: