Question

给表结构，如：

ID      ParentID      Name
1       NULL          A root
2       NULL          Another root
3       1             Child of 1
4       3                Grandchild of 1
5       4                   Great grandchild of 1
6       1             Child of 1
7       NULL          Another root
8       7             Child of 6

我正在为单个Sql语句/函数寻找一个优雅的（如果可能的话）解决方案，当给定ID = 1时，它将返回表中的所有数据

所以我的结果看起来像是：

ID      ParentID      Name
1       NULL          A root
3       1             Child of 1
4       3                Grandchild of 1
5       4                   Great grandchild of 1
6       1             Child of 1

我在SO上看过类似的问题，但大多数情况下他们似乎只是在看一定数量的关卡。

这种结构最终可能是无限的 - 带有孩子的文件夹，以及许多其他孩子

这可能吗？如果是这样，我将如何完成它？

Answer 1

所以引用这个答案：

<强> Sql Server CTE Parent Child recursive

以下是您的架构的工作版本：

表创建脚本

CREATE TABLE YOUR_TABLE
    ([ID] int, [ParentID] int, [Name] varchar(21))
;

INSERT INTO YOUR_TABLE
    ([ID], [ParentID], [Name])
VALUES
    (1, NULL, 'A root'),
    (2, NULL, 'Another root'),
    (3, 1, 'Child of 1'),
    (4, 3, 'Grandchild of 1'),
    (5, 4, 'Great grandchild of 1'),
    (6, 1, 'Child of 1'),
    (7, NULL, 'Another root'),
    (8, 7, 'Child of 6')
;

递归CTE

DECLARE @ID INT = 1

;WITH ParentChildCTE
AS (
    SELECT ID, ParentId, Name        
    FROM YOUR_TABLE
    WHERE Id = @ID

    UNION ALL

    SELECT T1.ID, T1.ParentId, T1.Name        
    FROM YOUR_TABLE T1
    INNER JOIN ParentChildCTE T ON T.ID = T1.ParentID
    WHERE T1.ParentID IS NOT NULL
    )
SELECT *
FROM ParentChildCTE

关键部分位于CTE创建中UNION ALL重新加入结果集，将ID加入ParentId，这不会限制数量水平。

Answer 2

您需要的是递归查询。 This Microsoft Technet example完全符合您的要求，但在示例中，我们要求的是员工层次结构，而不是文件夹。

从链接页面：

-- Create an Employee table.
CREATE TABLE dbo.MyEmployees
(
EmployeeID smallint NOT NULL,
FirstName nvarchar(30)  NOT NULL,
LastName  nvarchar(40) NOT NULL,
Title nvarchar(50) NOT NULL,
DeptID smallint NOT NULL,
ManagerID int NULL,
 CONSTRAINT PK_EmployeeID PRIMARY KEY CLUSTERED (EmployeeID ASC) 
);
-- Populate the table with values.
INSERT INTO dbo.MyEmployees VALUES 
 (1, N'Ken', N'Sánchez', N'Chief Executive Officer',16,NULL)
,(273, N'Brian', N'Welcker', N'Vice President of Sales',3,1)
,(274, N'Stephen', N'Jiang', N'North American Sales Manager',3,273)
,(275, N'Michael', N'Blythe', N'Sales Representative',3,274)
,(276, N'Linda', N'Mitchell', N'Sales Representative',3,274)
,(285, N'Syed', N'Abbas', N'Pacific Sales Manager',3,273)
,(286, N'Lynn', N'Tsoflias', N'Sales Representative',3,285)
,(16,  N'David',N'Bradley', N'Marketing Manager', 4, 273)
,(23,  N'Mary', N'Gibson', N'Marketing Specialist', 4, 16);

然后

WITH DirectReports (ManagerID, EmployeeID, Title, DeptID, Level)
AS
(
-- Anchor member definition
    SELECT e.ManagerID, e.EmployeeID, e.Title, edh.DepartmentID, 
        0 AS Level
    FROM dbo.MyEmployees AS e
    INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
        ON e.EmployeeID = edh.BusinessEntityID AND edh.EndDate IS NULL
    WHERE ManagerID IS NULL
    UNION ALL
-- Recursive member definition
    SELECT e.ManagerID, e.EmployeeID, e.Title, edh.DepartmentID,
        Level + 1
    FROM dbo.MyEmployees AS e
    INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
        ON e.EmployeeID = edh.BusinessEntityID AND edh.EndDate IS NULL
    INNER JOIN DirectReports AS d
        ON e.ManagerID = d.EmployeeID
)
-- Statement that executes the CTE
SELECT ManagerID, EmployeeID, Title, DeptID, Level
FROM DirectReports
INNER JOIN HumanResources.Department AS dp
    ON DirectReports.DeptID = dp.DepartmentID
WHERE dp.GroupName = N'Sales and Marketing' OR Level = 0;
GO

，结果是

ManagerID EmployeeID Title                         Level
--------- ---------- ----------------------------- ------
NULL      1          Chief Executive Officer       0
1         273        Vice President of Sales       1
273       16         Marketing Manager             2
273       274        North American Sales Manager  2
273       285        Pacific Sales Manager         2
16        23         Marketing Specialist          3
274       275        Sales Representative          3
274       276        Sales Representative          3
285       286        Sales Representative          3

选择语句以返回父级和无限子级

2 个答案:

表创建脚本

递归CTE