Question

是否可以将参数传递给选择节点的CTE，然后选择其父级到parentId为空的根？

在下面的代码中，如果我传入一个选择Rain Coats的参数，然后将树递归到其parentId为空的男装，并选择该分支中的所有节点，包括子节点。请有人帮我这个。我的例子只是递归并显示深度

SQL示例：

DECLARE @Department TABLE
(
    Id INT NOT NULL,
    Name varchar(50) NOT NULL,
    ParentId int NULL
)

INSERT INTO @Department SELECT 1, 'Toys', null
INSERT INTO @Department SELECT 2, 'Computers', null
INSERT INTO @Department SELECT 3, 'Consoles', 2
INSERT INTO @Department SELECT 4, 'PlayStation 3', 3
INSERT INTO @Department SELECT 5, 'Xbox 360', 2
INSERT INTO @Department SELECT 6, 'Games', 1
INSERT INTO @Department SELECT 7, 'Puzzles', 6
INSERT INTO @Department SELECT 8, 'Mens Wear', null
INSERT INTO @Department SELECT 9, 'Mens Clothing', 8
INSERT INTO @Department SELECT 10, 'Jackets', 9
INSERT INTO @Department SELECT 11, 'Rain Coats', 10

;WITH c 
AS
(
    SELECT Id, Name,1 AS Depth
    FROM @Department
    WHERE ParentId is null  

         UNION ALL

         SELECT t.Id, t.Name, c.Depth + 1 AS 'Level'
    FROM @Department T  
    JOIN c ON t.ParentId = c.Id

)
SELECT * FROM c WHERE c.Id = 3

Answer 1

您当前的CTE只显示树中的所有项目，包括Depth和所有其他属性。因此，它工作正常。

要做你正在寻找的东西，你必须几乎“反转”CTE - 首先抓住你感兴趣的项目，作为你的CTE的“锚”，然后“递归”到根：

DECLARE @StartID INT = 11

;WITH c 
AS
(
    SELECT Id, ParentId, Name, 1 AS Depth
    FROM @Department
    WHERE Id = @startID

    UNION ALL

    SELECT t.Id, t.ParentId, t.Name, c.Depth + 1 AS 'Level'
    FROM @Department T  
    INNER JOIN c ON t.Id = c.ParentId
)
SELECT * 
FROM c

这将完成您正在寻找和输出的内容：

Id ParentId  Name            Depth
11    10     Rain Coats        1
10     9     Jackets           2
 9     8     Mens Clothing     3
 8   NULL    Mens Wear         4

<强>更新

对于深度的反向顺序，您可以使用：

;WITH c 
AS
(
    SELECT Id, ParentId, Name, 1 AS Depth
    FROM @Department
    WHERE Id = @startID

    UNION ALL

    SELECT t.Id, t.ParentId, t.Name, c.Depth + 1 AS 'Level'
    FROM @Department T  
    INNER JOIN c ON t.Id = c.ParentId
)
SELECT Id,
       ParentID, 
       Name,
       MAX(Depth) OVER() - Depth + 1 AS InverseDepth
FROM c

此输出：

Id ParentId  Name            InverseDepth
11    10     Rain Coats        4
10     9     Jackets           3
 9     8     Mens Clothing     2
 8   NULL    Mens Wear         1

Answer 2

目前，您的CTE将root作为其锚点，并在其递归部分中从父级转换为子级。如果你想要整棵树，你需要从感兴趣的孩子开始，然后继续前进。这是一种方法。我引入了一个新的列StartingId，当我们走上树时，它仍保持不变 - 这是我们将根据以下内容选择的：

;WITH c 
AS
(
    SELECT Id AS StartingId, Id, ParentId, Name, 0 AS Height
    FROM @Department

    UNION ALL

    SELECT c.StartingId, p.Id, p.ParentId, p.Name, c.Height + 1 AS Height
    FROM @Department p INNER JOIN c ON p.Id = c.ParentId
)
SELECT * FROM c WHERE c.StartingId = 11

给出

StartingId  Id          ParentId    Name                                   Height
----------- ----------- ----------- ----------------------------------------------
11          11          10          Rain Coats                             0
11          10          9           Jackets                                1
11          9           8           Mens Clothing                          2
11          8           NULL        Mens Wear                              3

SQL Server CTE选择单个树分支结构到根

2 个答案: