sql-server - 获得单亲，所有 child 排成一排

Question

假设我在 SQL (server 2005) 中设置了一个父子结构:

CREATE TABLE parent (Id INT IDENTITY PRIMARY KEY, Name VARCHAR(255))
CREATE TABLE child (Id INT IDENTITY PRIMARY KEY, parentId INT, Name VARCHAR(255))

insert into parent select 'parent with 1 child'
insert into parent select 'parent with 2 children'

insert into child(name, parentid) select 'single child of parent 1', 1
insert into child(name, parentid) select 'child 1 of 2 of parent 2', 2
insert into child(name, parentid) select 'child 2 of 2 of parent 2', 2

有没有办法为每个父项返回一行，并将其子项作为列？喜欢:

parent.Id, parent.Name, child(1).Id, child(1).Name, child(2).Id, child(2).Name

开始于:

select * from parent p
    left outer join child c1 on c1.parentid = p.id

Answer 1

您的示例接近旋转，但我认为旋转功能不适用于此示例。

为了保持理智，我已将您的示例重命名为使用“部门人员”，而不是“ child parent ”。

所以，首先是表格和一些数据

DECLARE @Department TABLE
  ( 
   DepartmentID int
  ,DepartmentName varchar(50)
  )
DECLARE @Person TABLE
  ( 
   PersonID int
  ,PersonName varchar(50)
  ,DepartmentID int
  )

INSERT  INTO @Department
  ( DepartmentID, DepartmentName )
 SELECT 1, 'Accounting' UNION
 SELECT 2, 'Engineering' UNION
 SELECT 3, 'Sales' UNION
 SELECT 4, 'Marketing' ;

INSERT  INTO @Person
  ( PersonID, PersonName, DepartmentID )
 SELECT 1, 'Lyne', 1 UNION
 SELECT 2, 'Damir', 2 UNION
 SELECT 3, 'Sandy', 2 UNION
 SELECT 4, 'Steve', 3 UNION
 SELECT 5, 'Brian', 3 UNION
 SELECT 6, 'Susan', 3 UNION
 SELECT 7, 'Joe', 4 ;

现在我想展平模型，我将使用临时表，因为我有表变量——但是“真实表”上的 View 也不错。

/*  Create a table with:
    DepartmentID, DepartmentName, PersonID, PersonName, PersonListIndex

 This could be a view instead of temp table. 
*/
IF object_id('tempdb.dbo.#tmpTbl','U') IS NOT NULL
 DROP TABLE #tmpTbl

;
WITH  prs
        AS ( SELECT PersonID
                   ,PersonName
                   ,DepartmentID
                   ,row_number() OVER ( PARTITION BY DepartmentID ORDER BY PersonID ) AS [PersonListIndex]
             FROM   @Person
           ),
      dptprs
        AS ( SELECT d.DepartmentID
                   ,d.DepartmentName
                   ,p.PersonID 
                   ,p.PersonName
                   ,p.PersonListIndex
             FROM   @Department AS d
                    JOIN prs AS p ON p.DepartmentID = d.DepartmentID
           )
SELECT * INTO #tmpTbl FROM dptprs

-- SELECT * FROM #tmpTbl

动态列就是动态查询，我会逐行组成一个表

/* Table to compose dynamic query */
DECLARE @qw TABLE
  ( 
   id int IDENTITY(1, 1)
  ,txt nvarchar(500)
  )

/* Start composing dynamic query */
INSERT  INTO @qw ( txt ) VALUES  ( 'SELECT' ) 
INSERT  INTO @qw ( txt ) VALUES  ( '[DepartmentID]' )
INSERT  INTO @qw ( txt ) VALUES  ( ',[DepartmentName]' ) ;


/* fetch max number of employees in a department */
DECLARE @i int ,@m int
SET @m = (SELECT max(PersonListIndex) FROM #tmpTbl)

/* Compose dynamic query */
SET @i = 1
WHILE @i <= @m 
  BEGIN  
      INSERT  INTO @qw ( txt )
            SELECT  ',MAX(CASE [PersonListIndex] WHEN '
                    + cast(@i AS varchar(10)) + ' THEN [PersonID] ELSE NULL END) AS [Person_'
                    + cast(@i AS varchar(10)) + '_ID]'

      INSERT  INTO @qw ( txt )
            SELECT  ',MAX(CASE [PersonListIndex] WHEN '
                    + cast(@i AS varchar(10)) + ' THEN [PersonName] ELSE NULL END) AS [Person_'
                    + cast(@i AS varchar(10)) + '_Name]'  

    SET @i = @i + 1
  END

/* Finish the dynamic query */
INSERT  INTO @qw (txt) VALUES ( 'FROM #tmpTbl' )
INSERT  INTO @qw (txt) VALUES ( 'GROUP BY [DepartmentID], [DepartmentName]' )
INSERT  INTO @qw (txt) VALUES ( 'ORDER BY [DepartmentID]' )

-- SELECT * FROM @qw

现在，将所有查询行连接到一个变量中并执行

/* Create a variable with dynamic sql*/
DECLARE @exe nvarchar(4000)
SET @exe=''
SELECT  @exe = @exe + txt + ' ' FROM @qw ORDER BY id

/* execute dynamic sql */
EXEC master..sp_executesql @exe

结果如下: