SQL Server 的 Select 语句中的递归

Question

我有三个 SQL Server 表：Projects、ProjectTree、ProjectTreeRec。

Projects 类似于目录，我试图在名为Standard Parts 的目录下查找所有子目录。显然这里需要递归。

Projects 表具有以下列：

ProjectID, Name, Deleted

ProjectTree 表具有以下列：

ProjectID, ChildProject

我认为我不需要ProjectTreeRec 表作为这项工作的一部分，但它包含ChildProjectID、ParentProjectID、Level 列。

我想开发一个递归选择语句来查找Standard Parts目录下所有未被删除的子目录（不是1，而是0）。

我是 CTE 和递归的新手。我得到了一些结果，但不是我所追求的。

这是非递归调用，它找到了我的第一级，但没有更深入。它工作正常。

SELECT 
    '(Directory Not Available)'

UNION

SELECT DISTINCT
    C.[Name] 
FROM 
    [EPDM].[dbo].[Projects] A
JOIN 
    [EPDM].[dbo].[ProjectTree] B ON B.ProjectID = A.ProjectID 
JOIN 
    [EPDM].[dbo].[Projects] C ON B.childproject = C.projectid 
WHERE
    A.name = 'Standard Part Library' 
    AND A.[Deleted] = 0;

欢迎任何帮助。

Answer 1

我会尝试以下类似的方法来评估树结构，然后将 cte 加入您的表以获得名称：

DECLARE @SearchProjectID int = 1;

WITH cteTree AS(
SELECT ProjectID, ChildProject
  FROM ProjectTree
  WHERE ProjectID = @SearchProjectID
UNION ALL
SELECT pt.ProjectID, pt.ChildProject
  FROM ProjectTree AS pt
  JOIN cteTree AS ct ON ct.ChildProject = pt.ProjectID
)
SELECT *
  FROM cteTree

Answer 2

请试试这个...

  CREATE TABLE #Project
(
ProjectID INT 
,Name varchar(50)
,Deleted bit
)

CREATE TABLE #ProjectTree
(
ProjectID INT, 
ChildProject INT
)

INSERT INTO #Project
(ProjectID,Name,Deleted)
SELECT 1,'Standard Part Library',0
UNION ALL SELECT 2,'P2',1
UNION ALL SELECT 3,'P3',0
UNION ALL SELECT 4,'P4',0

INSERT INTO #ProjectTree
(ProjectID,ChildProject)
SELECT 1,3
UNION SELECT 2,4

SELECT * FROM #Project
SELECT * FROM #ProjectTree

;WITH CTE_Project 
AS
(
SELECT 
	A.ProjectId
	,B.ChildProject
	,A.Name AS ProjectName
FROM #Project A
	INNER JOIN #ProjectTree B
		ON A.ProjectId = B.ProjectId
WHERE
	A.Name = 'Standard Part Library' 
	AND A.[Deleted] = 0

UNION ALL

SELECT 
	PT.ProjectID
	,PT.ChildProject
	,CP.ProjectName AS ProjectName
FROM 
	#ProjectTree AS PT
	INNER JOIN CTE_Project CP 
		ON PT.ChildProject = CP.ProjectID
)
SELECT 
ProjectName
,ProjectId
,ChildProject
FROM 
CTE_Project;