Question

当我发送CatelogID时，需要使用rootcatelogName和RootCatelogID获取catelogID

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当我将CatelogID设为6时，输出应该是这样的

O / P：

CREATE TABLE catelog 
 (
 CatelogID BIGINT IDENTITY(1,1),
 CatelogName NVARCHAR(50) NOT NULL,
 ParentID BIGINT NULL
 )

SELECT * from catelog

INSERT INTO catelog(catelogName,ParentID)
VALUES('Embedded Sytem',NULL),
('Library',NULL),
('Books',2),
('Pages',3),
('Chapters',4),
('Paragraph',5),
('New Sytem',1),
('College',NULL)

如果我没有传递任何值，我可以得到像这样的结果

CatelogID  RootCatelogName RootParentID 

  2          Library        NULL
  6          Library        2

Answer 1

尝试层次结构CTE

DECLARE @id INT = 6;

WITH h AS (
  SELECT CatelogID,catelogName,ParentID
  FROM catelog
  WHERE CatelogID = @id
  UNION ALL
  SELECT p.CatelogID,p.catelogName,p.ParentID
  FROM h
  JOIN catelog p ON p.CatelogID = h.ParentID
)
SELECT t.* 
FROM h
CROSS APPLY (
  SELECT @ID AS catelogID, catelogName AS RootCatelogName, CatelogID AS RootParentID 
  UNION 
  SELECT CatelogID, catelogName AS RootCatelogName, ParentID AS RootParentID 
  ) t
WHERE ParentID IS NULL;

返回

    catelogID   RootCatelogName RootParentID
        2       Library         NULL
        6       Library         2

修改

回答第二个问题的查询

WITH h AS ( SELECT CatelogID AS leafId, CatelogID, catelogName, ParentID FROM catelog WHERE ParentID IS NOT NULL UNION ALL SELECT h.leafId, p.CatelogID, p.catelogName, p.ParentID FROM h JOIN catelog p ON p.CatelogID = h.ParentID ) SELECT leafId AS catelogID, catelogName AS RootCatelogName, CatelogID AS RootParentID FROM h WHERE ParentID IS NULL UNION ALL SELECT CatelogID,catelogName,ParentID FROM catelog WHERE ParentID IS NULL ORDER BY CatelogID;

返回

catelogID RootCatelogName RootParentID 1 Embedded Sytem NULL 2 Library NULL 3 Library 2 4 Library 2 5 Library 2 6 Library 2 7 Embedded Sytem 1 8 College NULL

Answer 2

使用递归CTE和row_number来获得最高级别：

declare @CatelogID BIGINT = 6;

;with cte as 
( 
    select CatelogID as BaseCatelogID, CatelogName as BaseCatelogName, 0 as level, CatelogID, CatelogName, ParentID 
    from catelog t
    where CatelogID = @CatelogID

    union all

    select cte.BaseCatelogID, cte.BaseCatelogName, level + 1, t.CatelogID, t.CatelogName, t.ParentID 
    from cte
    join catelog t on (cte.ParentID = t.CatelogID)
)
, cte2 as
(
    select *, row_number() over (partition by BaseCatelogID order by level desc) as rn 
    from cte
)
select CatelogID, CatelogName as RootCatelogName, ParentID as RootParentID
from cte2 where rn = 1
union all
select BaseCatelogID, CatelogName, CatelogID
from cte2 where rn = 1;

返回：

CatelogID  RootCatelogName RootParentID 
  2          Library        NULL
  6          Library        2

获取子行及其顶部根行，并以特殊方式组合ID和名称

2 个答案: