遞歸CTE返回路徑中的所有連接節點

Question

我有一張表，它通過將兩個「節點」鏈接在一起來創建路徑。

Node 
----------- 
Id - Primary Key 
Name 
etc... 


Path 
------ 
Id - Primary Key 
From - FK to Node 
To - FK to Node 

所以這個路徑：

W --- X --- Y --- Z 

可以建這樣的：

Node 
Id Name 
--- ----- 
1 W 
2 X 
3 Y 
4 Z 
5 A 
6 B 
7 C 


Path 
Id From  To 
--- ------- ------- 
1 1  2 
2 2  3 
3 3  4 
4 6  7 

我想出了給定任何節點ID遞歸CTE查詢，遍歷的路徑和返回所有涉及的「路徑」。

declare @nodeId = 2 
;WITH cte AS (

    -- ANCHOR 
    -- Find one path involving Node 
    SELECT top 1 p.*, 0 as [Seq] FROM dbo.Path p WHERE [From] = @nodeId or [To] = @nodeId 

    union all 

    -- go left 
    select leftPath.*, cte.[Seq] - 1 as [Seq] 
    from [Path] leftPath 
    join cte on cte.[From] = leftPath.[To] and cte.[Seq] <= 0 

    union all 

    -- go right 
    select rightPath.*, cte.[Seq] + 1 as [Seq] 
    from [Path] rightPath 
    join cte on cte.[To] = rightPath.[From] and cte.[Seq] >= 0 
) 

SELECT cte.Id, cte.Seq, cte.From, cte.To 
FROM cte 
order by [Seq] 

因此，這將返回所有路徑 -

Path 
Id Seq From  To 
--- --- ------- ------- 
1 -1 1  2 
2 0 2  3 
3 1 3  4 

但我怎麼能寫出給定的節點ID之一的查詢，穿越的路徑，左，右，並返回所有不同（有序）涉及的節點？

Id Name 
    --- ----- 
    1 W 
    2 X 
    3 Y 
    4 Z 

Answer 1

我想說的是這樣的：

DECLARE @nodeId int = 2; 

select 
* 
from Node t1 
inner join Path t2 
on t1.Id = t2.[From] or t1.Id = t2.[To] 
where t1.Id = @nodeId 
order by t1.Id 

我知道，上面的查詢不能解決你的問題，但是，這個查詢你得到了相同的結果比用CTE和更簡單。從這個查詢中查詢結果如果查詢還沒有結果，你期望的結果是什麼。

但我明白這不是你想要的。爲此，我需要一個完整的結果示例，我讀的最後一個段落是表節點。 ¿？

Answer 2

這會返回您想要的結果，但對於@nodeId int = 5;的情況，它不返回任何內容，因爲沒有與該節點關聯的路徑。

見我從cte.[From]得到Name's，然後從最後 ID cte.[To]

我添加源再添Name，以確保訂單是您在輸出顯示的一個。否則因爲屬於同一行的最後兩個Name's可能會有倒序。

SQL DEMO

;WITH cte AS (

    -- ANCHOR 
    -- Find one path involving Node 
    SELECT top 1 p.*, 0 as [Seq] FROM dbo.Path p WHERE [From] = @nodeId or [To] = @nodeId order by [From] desc 

    union all 

    -- go left 
    select leftPath.*, cte.[Seq] - 1 as [Seq] 
    from [Path] leftPath 
    join cte on cte.[From] = leftPath.[To] and cte.[Seq] <= 0 

    union all 

    -- go right 
    select rightPath.*, cte.[Seq] + 1 as [Seq] 
    from [Path] rightPath 
    join cte on cte.[To] = rightPath.[From] and cte.[Seq] >= 0 
) 

SELECT 'A' as [Source], cte.Id, cte.Seq, cte.[From], cte.[To], Node.[Name] 
FROM cte 
JOIN Node 
    ON cte.[From] = Node.[Id] 
UNION 
SELECT 'B' as [Source], cte.Id, cte.Seq, cte.[From], cte.[To], Node.[Name] 
FROM cte 
JOIN Node 
    ON cte.[To] = Node.[Id] 
WHERE cte.id = (SELECT Max(Id) FROM cte) 

order by [Source], [Seq] 

OUTPUT

@nodeId int = 1 to 4 same result: 

@nodeId int = 6 to 7 same result: 

如果你把前面的查詢也CTE，並呼籲step2你可以有你的願望格式是這樣的：

SELECT ROW_NUMBER() OVER (ORDER BY [Source], [Seq]) as [Id], 
     Name 
FROM step2 

最終輸出