sql：重复行和所有相关行答案

【问题标题】：sql : duplicate row and all related rowssql：重复行和所有相关行
【发布时间】：2014-09-15 22:40:26
【问题描述】：

我有以下 3 个相关的表

Schools           Departments          Classes
---------------   ------------------   -----------------
ID                ID                   ID
School_Name       ID_Schools           ID_Departments
                  Department_Name      Class_Name

以及关于它们包含的内容的一些示例（我会尽可能地画出最好的）

---- Schools ---
ID   School_Name
----------------
 1   School_1  <----------------------\
 2   School_2                         |
 n   ........                         |
                                      |
---- Departments ----------------     |
ID   ID_Schools   Department_Name     |
---------------------------------     |
 1            1   Dept_1  <-----------/ -->--\
 2            1   Dept_2  <-----------/ -->--|------\
 3            2   Dept_1                     |      |
 n           ..   ......                     |      |
                                             |      |
---- Classes -------------------             |      |
ID   ID_Departments   Class_Name             |      |
--------------------------------             |      |
 1                1   Class_1  <-------------/      |
 2                1   Class_2  <-------------/      |
 3                1   Class_3  <-------------/      |
 4                2   Class_1  <--------------------/
 n               ..   .......

所有 ID 都是自动递增的

我正在寻找一种复制“School_1”层次结构的方法。问题是我如何维护新行之间的关系？

例如，要复制“School_1”层次结构，我将在 Schools 表中插入一个新的原始数据，最终将生成一个新 ID（例如 5）。

---- Schools ---
ID   School_Name
----------------
 5   School_1

属于“School_1”的部门“Dept_1”和“Dept_2”将获得新 ID

---- Departments ----------------
ID   ID_Schools   Department_Name
---------------------------------
16            5   Dept_1
17            5   Dept_2

类也将获得新的 ID

---- Classes -------------------
ID   ID_Departments   Class_Name
--------------------------------
56               16   Class_1
57               16   Class_2
58               16   Class_3
59               17   Class_1

我怎样才能以一种简单而聪明的方式实现这一点？

【问题讨论】：

现在无法回答这个问题，但投票赞成问题的完美形式。我希望所有 SO 问题都像这个问题一样清晰易懂！

标签： sql sql-server sql-server-2012

【解决方案1】：

复制学校和部门很容易。要复制课程，我们需要一个函数，它可以根据新旧 school.id 值将旧部门 ID 转换为新部门 ID。

如果 Dept_id 和 Dept_name 的组合是唯一的，则可以采用以下方法：

DECLARE @old_id int; // set it 

DECLARE @school_id int;
DECLARE @school_name varchar(100); 

SET @school_name = (SELECT school_name from schools where id = @old_id);

INSERT into schools (school_name)
  OUTPUT Inserted.id into @school_id
  VALUES (@school_name);

INSERT into departments (id_schools, department_name)
  SELECT @school_id, department_name 
    FROM departments 
      WHERE id_schools = @old_id;

INSERT into classes (ID_Departments, Class_Name)
  SELECT
    (SELECT s.ID_Departments from departments s
       WHERE s.id_schools = @school_id and s.department_name = d.department_name),
    c.class_name
  FROM classes c, departments d
    WHERE c.ID_Departments = d.ID and d.ID_Schools = @old_id;

如果 (id_schools, department_name) 对不是唯一的，您可以将 department_id 值临时存储在 department_name 字段中并稍后更新（在创建课程之后）。

【讨论】：

【解决方案2】：

为此，我尝试编写一个简单的存储过程。我没有时间测试它的逻辑，但我认为它可以给出我对这个问题的思考方式。测试一下...

CREATE PROCEDURE [dbo].[copySchoolHierarchy] (@SchoolId As Int) 
As Begin

BEGIN TRANSACTION

BEGIN TRY

    DECLARE @tmpSchoolName NVARCHAR(100),
            @tmpNewSchoolID INT

    --First insert into schools
    SELECT @tmpSchoolName = School_Name FROM Schools WHERE ID = @SchoolId 
    INSERT INTO SCHOOLS (School_Name) VALUES (@tmpSchoolName)
    SELECT @tmpNewSchoolID = SCOPE_IDENTITY()

    --Then get the departments
    INSERT INTO Departments (ID_Schools, Department_Name)
    SELECT @tmpNewSchoolID AS someId, Department_Name FROM DEPARTMENTS Where ID_Schools = @SchoolId

    --and the classes
    INSERT INTO Classes (ID_Departments, Class_Name)
    SELECT C.ID_Departments, C.Class_Name FROM Classes C 
    INNER JOIN DEPARTMENTS D ON C.ID_Departments = D.ID
    WHERE D.ID_Schools = @tmpNewSchoolID 

    COMMIT TRANSACTION
END TRY
BEGIN CATCH
    --Raise some exception here...

    ROLLBACK TRANSACTION
END CATCH
END

【讨论】：

【解决方案3】：

我建议使用 SQL INSERT AS SELECT 魔法，如下所述：Insert into ... values ( SELECT ... FROM ... )。

让您的旧 School ID 为 7，新 School ID 为 17，然后您可以为每个表创建一个查询为 INSERT INTO Departments(id, id_schools, name) VALUES (NULL, 17, (SELECT name FROM Departments WHERE id_schools = 17))。

当您需要按部门（包含多个部门）插入班级时会有点棘手，但您可以手动填写 WHERE id_departments IN (5,6,13, etc) 或自动填写为 WHERE id_departments IN (SELECT id FROM Departments WHERE School_ID = 17)

P.S.：这更像是建议而不是答案，因此 SQL 方言或代码质量等一些细节可能不合适，但我确信方法本身。

【讨论】：