将根节点添加到SQL CTE层次结构树

Question

我的查询工作基于CTE Recursion to get tree hierarchy显示了我的层次结构树。

结果看起来像

- Category 
- Category 
- - SubCategory 
- - - Sub SubCategory 
- - SubCategory 
... 

我想根节点添加到我的树，但我没有看到如何做到这一点。我如何将根节点添加到这棵树？

编辑：我目前的查询看起来是这样的：

;WITH Tree as 
(
    Select Parent_ID, ParentDescr, Node_ID, Node, 1 as Level, cast(Node as varchar(max)) as Path 
    FROM Nodes 
    WHERE ParentDescr = 'Root' 

    UNION ALL 

    Select A.Parent_ID, A.ParentDescr, A.Node_ID, A.Node, Level + 1 as Level, cast(B.Path + ' | ' + A.Node as varchar(max)) as Path 
    FROM Nodes A 
    INNER JOIN Tree B ON A.PARENT_ID = B.Node_ID 
    WHERE A.ParentDescr <> 'Root' 
) 
SELECT REPLICATE(' - ', level) + Node as Tree, Path, Node_ID, ParentDescr, PARENT_ID 
from Tree 
ORDER BY Path asc 

下面是一些样本数据：

SELECT * 
FROM (
VALUES 
('123','Root',NULL,NULL), 
('456','Category','123','Root'), 
('789','SubCategory','456','Category'), 
('012','Sub SubCategory','789','SubCategory'), 
('345','Category','123','Root')) AS vtable 
([Class_ID],[Class],[Parent_ID],[ParentClass]) 

结果应该是这样的：

Root 
- Category 
- - SubCategory 
- - - Sub SubCategory 
- Category 

Answer 1

其实，我想你只需要改变这一点：

WHERE ParentDescr = 'Root' 

要这样：

WHERE Node = 'Root' 

，同样，改变这种：

WHERE A.ParentDescr <> 'Root' 

要这样：

WHERE A.Node <> 'Root' 

编辑：

根据您的样本数据，我的改变应该有工作d如果你正确实施它们。验证您的新查询是这样的：

;WITH Tree as 
(
    Select Parent_ID, ParentDescr, Node_ID, Node, 1 as Level, cast(Node as varchar(max)) as Path 
    FROM Nodes 
    WHERE Node = 'Root' 

    UNION ALL 

    Select A.Parent_ID, A.ParentDescr, A.Node_ID, A.Node, Level + 1 as Level, cast(B.Path + ' | ' + A.Node as varchar(max)) as Path 
    FROM Nodes A 
    INNER JOIN Tree B ON A.PARENT_ID = B.Node_ID 
    WHERE A.Node <> 'Root' --this line really isn't even necessary 
) 
SELECT REPLICATE(' - ', level) + Node as Tree, Path, Node_ID, ParentDescr, PARENT_ID 
from Tree 
ORDER BY Path asc 

它应该工作。