Question

我有两张桌子第一张桌子上有一所学校和分校的部门。如果Dept和ChildDept值为0，那么它就是一个部门。如果Dept与0不同，则它是部门的分支。 ParentDept，Dept和ChildDept值与deptID无关。他们只是按照我的理解进行练级。

表：部门

    deptID     ParentDept     Dept     ChildDept Active Department
----------+--------------+--------+-------------+------+--------
       100|             1|       0|            0|     1|Education
       200|             1|       1|            0|     1|Primary School
       300|             1|       2|            0|     1|Primary Science
       315|             2|       0|            0|     1|Arts
       517|             2|       1|            0|     1|Painting
       518|             2|       2|            0|     1|Music
       555|             2|       3|            0|     0|Dance

第二个表包含学生信息

表：学生

    studID         deptID  
----------+--------------- 
         1|            300
         2|            200
         3|            517
         4|            200
         5|            300
         6|            517
         7|            518

我编写了一个SQL查询，可以获取每个部门的学生计数：

SELECT d.Department,
       (SELECT COUNT(s.studID) 
        FROM Students AS s 
        WHERE d.deptID = s.deptID) AS studentCount,

       (SELECT Department 
        FROM Departments 
        WHERE deptID = ParentDept) AS ParentDeptName
FROM Departments AS d 
WHERE d.Active = 1

结果表格如下：

Department      studentCount ParentDeptName
---------------+------------+--------------
Primary Science|           2|Education
Primary School |           2|Education
Painting       |           2|Education
Music          |           1|Education

如你所见＆＃39;绘画＆＃39;和音乐＆＃39;分支机构属于＆＃39; Arts＆＃39;部门但查询结果显示＆＃39;教育＆＃39;对于每一行的父系都是错的。它应该像

Department      studentCount ParentDeptName
---------------+------------+--------------
Primary Science|           2|Education
Primary School |           2|Education
Painting       |           2|Arts
Music          |           1|Arts

这个查询或我有什么问题？

Answer 1

试试这个：

SELECT d.Department,
   (SELECT COUNT(s.studID) 
    FROM Students AS s 
    WHERE d.deptID = s.deptID) AS studentCount,
   de.Departments AS ParentDeptName
FROM Departments AS d left join Departments AS de on d.ParentDept = de.deptID 
WHERE d.Active = 1

Answer 2

Check Out My Fiddle我不知道我将如何计算：（

SELECT (Select Department from Departments a where a.deptID = Departments.ParentDept) As ParentDEPTS,
(Select Department from Departments b where b.deptID = Students.deptID) As StudentDEPTS,  Students.studID AS STUIDS
 FROM Departments
 LEFT JOIN Students
ON Departments.deptID=Students.deptID 
Where 
    Departments.ParentDept is not null 
    AND 
    Students.deptID is not null
    AND 
    Departments.Active =1;

Answer 3

让我们制作一些测试数据：

DECLARE @Dept TABLE
(
    deptID INT,
    ParentDept INT,
    Dept INT,     
    ChildDept INT,
    Active INT, 
    Department VARCHAR(50)
)

INSERT INTO @Dept
VALUES
(100, 1, 0, 0, 1, 'Education'),
(200, 1, 1, 0, 1, 'Primary School'),
(300, 1, 2, 0, 1, 'Primary Science'),
(315, 2, 0, 0, 1, 'Arts'),
(517, 2, 1, 0, 1, 'Painting'),
(518, 2, 2, 0, 1, 'Music'),
(555, 2, 3, 0, 0, 'Dance');

DECLARE @Student TABLE
(
    studID INT,
    deptID INT
)

INSERT INTO @Student
VALUES
(1, 300),
(2, 200),
(3, 517),
(4, 200),
(5, 300),
(6, 517),
(7, 518);

现在我们要加入学生部门，然后部门加入家长部门并将他们分组以获得我们的结果：

SELECT 
    d.Department, 
    COUNT(*) RecCnt, 
    p.Department ParentDept 
FROM @Student s
INNER JOIN @Dept d
    ON s.deptID = d.deptID
INNER JOIN @Dept p
    ON p.ParentDept = d.ParentDept
    AND p.Dept = 0
GROUP BY d.Department, p.Department

这是输出：

Department  RecCnt  ParentDept
Music           1   Arts
Painting        2   Arts
Primary School  2   Education
Primary Science 2   Education

如何使用一个查询选择父子类别？

3 个答案: