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  • 一列保存多个ID(将多个用逗号、特殊符号 隔开的ID转换成用逗号隔开的名称)

    背景:在做项目时,经常会遇到这样的表结构在主表的中有一列保存的是用逗号隔开ID。如,当一个员工从属多个部门时、当一个项目从属多个城市时、当一个设备从属多个项目时,很多人都会在员工表中加入一个deptIds VARCHAR(1000)列(本文以员工从属多个部门为例),用以保存部门编号列表(很明显这不符合第一范式,但很多人这样设计了,在这篇文章中我们暂不讨论在这种应用场景下,如此设计的对与错,有兴趣的可以在回复中聊聊),然后我们在查询列表中需要看到这个员工从属哪些部门。

    初始化数据:

    部门表、员工表数据:

    IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Department]'))
    DROP TABLE [dbo].Department
    GO
    --部门表
    CREATE TABLE Department
    (
        id int,
        name nvarchar(50)
    )
    INSERT INTO Department(id,name)
    SELECT 1,'人事部'
    UNION 
    SELECT 2,'工程部'
    UNION 
    SELECT 3,'管理部'
    
    SELECT * FROM Department
    
    
    IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Employee]'))
    DROP TABLE [dbo].Employee
    GO
    --员工表
    CREATE TABLE Employee
    (
        id int, 
        name nvarchar(20),
        deptIds varchar(1000)
    )
    INSERT INTO Employee(id,name,deptIds)
    SELECT 1,'蒋大华','1,2,3'
    UNION
    SELECT 2,'小明','1'
    UNION 
    SELECT 3,'小华',''
    
    SELECT * FROM Employee

    希望得到的结果:

    解决方法:

    第一步,是得到如下的数据。即将员工表集合与相关的部门集合做交叉连接,其中使用了fun_SplitIds函数(作用是将ids分割成id列表),然后员工集合与这个得到的集合做交叉连接

    SELECT E.*,ISNULL(D.name,'') AS deptName
    FROM Employee AS E 
       OUTER APPLY dbo.fun_SplitIds(E.deptIds) AS DID
       LEFT JOIN Department AS D ON DID.ID=D.id;

    第二步,已经得到了如上的数据,然后要做的就是根据ID分组,并对deptName列做聚合操作,但可惜的是SQL SERVER还没有提供对字符串做聚合的操作。但想到,我们处理树形结构数据时,用CTE来做关系数据,做成有树形格式的数据,如此我们也可以将这个问题转换成做树形格式的问题,代码如下:

    ;WITH EmployeT AS(
    --员工的基本信息(使用OUTER APPLY将多个ID拆分开来,然后与部门表相关联)
    --此时已将员工表所存的IDS分别与部门相关联,下面需要将此集合中的deptName聚合成一个记录
    SELECT E.*,ISNULL(D.name,'') AS deptName
    FROM Employee AS E 
       OUTER APPLY dbo.fun_SplitIds(E.deptIds) AS DID
       LEFT JOIN Department AS D ON DID.ID=D.id
    ),mike AS(
       SELECT id,name,deptIds,deptName
          ,ROW_NUMBER()OVER(PARTITION BY id ORDER BY id) AS level_num
       FROM EmployeT
    ),mike2 AS(
       SELECT id,name,deptIds,CAST(deptName AS NVARCHAR(100)) AS deptName,level_num 
       FROM mike
       WHERE level_num=1
       UNION ALL
       SELECT m.id,m.name,m.deptIds,CAST(m2.deptName+','+m.deptName AS NVARCHAR(100)) AS deptName,m.level_num 
       FROM mike AS m
          INNER JOIN mike2 AS m2 ON m.ID=m2.id AND m.level_num=m2.level_num+1
    ),maxMikeByIDT AS(
           SELECT id,MAX(level_num) AS level_num
           FROM mike2 
           GROUP BY ID
    )
    
    
    SELECT A.id,A.name,A.deptIds,A.deptName
    FROM mike2 AS A 
       INNER JOIN maxMikeByIDT AS B ON A.id=B.ID AND A.level_num=B.level_num
    ORDER BY A.id OPTION (MAXRECURSION 0)

    结果如下:

    全部SQL:

    IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Department]'))
    DROP TABLE [dbo].Department
    GO
    --部门表
    CREATE TABLE Department
    (
        id int,
        name nvarchar(50)
    )
    INSERT INTO Department(id,name)
    SELECT 1,'人事部'
    UNION 
    SELECT 2,'工程部'
    UNION 
    SELECT 3,'管理部'
    
    SELECT * FROM Department
    
    
    IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Employee]'))
    DROP TABLE [dbo].Employee
    GO
    --员工表
    CREATE TABLE Employee
    (
        id int, 
        name nvarchar(20),
        deptIds varchar(1000)
    )
    INSERT INTO Employee(id,name,deptIds)
    SELECT 1,'蒋大华','1,2,3'
    UNION
    SELECT 2,'小明','1'
    UNION 
    SELECT 3,'小华',''
    
    SELECT * FROM Employee
    
    --创建一个表值函数,用来拆分用逗号分割的数字串,返回只有一列数字的表
    IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[fun_SplitIds]'))
    DROP FUNCTION [dbo].fun_SplitIds
    GO
    CREATE FUNCTION dbo.fun_SplitIds(
        @Ids nvarchar(1000)
    )
    RETURNS @t_id TABLE (id VARCHAR(36))
    AS
    BEGIN
        DECLARE @i INT,@j INT,@l INT,@v VARCHAR(36);
        SET @i = 0;
        SET @j = 0;
        SET @l = len(@Ids);
        while(@j < @l)
        begin
           SET @j = charindex(',',@Ids,@i+1);
           IF(@j = 0) set @j = @l+1;
           SET @v = cast(SUBSTRING(@Ids,@i+1,@j-@i-1) as VARCHAR(36));
           INSERT INTO @t_id VALUES(@v)
           SET @i = @j;
        END
        RETURN;
    END
    GO
    
    
    ;WITH EmployeT AS(
    --员工的基本信息(使用OUTER APPLY将多个ID拆分开来,然后与部门表相关联)
    --此时已将员工表所存的IDS分别与部门相关联,下面需要将此集合中的deptName聚合成一个记录
    SELECT E.*,ISNULL(D.name,'') AS deptName
    FROM Employee AS E 
       OUTER APPLY dbo.fun_SplitIds(E.deptIds) AS DID
       LEFT JOIN Department AS D ON DID.ID=D.id
    ),mike AS(
       SELECT id,name,deptIds,deptName
          ,ROW_NUMBER()OVER(PARTITION BY id ORDER BY id) AS level_num
       FROM EmployeT
    ),mike2 AS(
       SELECT id,name,deptIds,CAST(deptName AS NVARCHAR(100)) AS deptName,level_num 
       FROM mike
       WHERE level_num=1
       UNION ALL
       SELECT m.id,m.name,m.deptIds,CAST(m2.deptName+','+m.deptName AS NVARCHAR(100)) AS deptName,m.level_num 
       FROM mike AS m
          INNER JOIN mike2 AS m2 ON m.ID=m2.id AND m.level_num=m2.level_num+1
    ),maxMikeByIDT AS(
           SELECT id,MAX(level_num) AS level_num
           FROM mike2 
           GROUP BY ID
    )
    
    
    SELECT A.id,A.name,A.deptIds,A.deptName
    FROM mike2 AS A 
       INNER JOIN maxMikeByIDT AS B ON A.id=B.ID AND A.level_num=B.level_num
    ORDER BY A.id OPTION (MAXRECURSION 0)
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  • 原文地址:https://www.cnblogs.com/kevin2013/p/2731009.html
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