问题
Hi I am trying to get the full hierarchy of my category. Here is my sample table
ID PARENT_ID NAME DEPTH
------------------------------------------
1 NULL A 1
2 NULL B 1
3 NULL C 1
4 1 D 2
5 4 E 3
The cte output should be this
ID PARENT_ID NAME
---------------------------
1 NULL A
2 NULL B
3 NULL C
4 1 D
5 4 E
5 1 E
As you can see id:5 is parent of 4 and 1. How do i query the whole tree
回答1:
DECLARE @tmp TABLE(ID INT,ParentID INT,NAME VARCHAR(10),DEPTH INT)
INSERT INTO @tmp VALUES
(1 ,NULL ,'A' ,1 ),
(2 ,NULL ,'B' ,1 ),
(3 ,NULL ,'C' ,1 ),
(4 ,1 ,'D' ,2 ),
(5 ,4 ,'E' ,3 ),
(6 ,5 ,'F' ,4 );
select * from @tmp
;WITH cte AS
(
SELECT A.ID
,A.ParentID
,A.NAME
,A.DEPTH
FROM @tmp A
UNION ALL
SELECT A.ID
,B.ParentID
,A.NAME
,A.DEPTH
FROM cte A
INNER JOIN @tmp B on A.ParentID = B.ID
WHERE B.ParentID IS NOT NULL
)
SELECT * FROM cte
回答2:
In SQL Server 2008 CTE can be use to query recursively.
Example of CTE from MSDN
-- Sample Solution (Untested)
;With TableCTE(Id, Name, ParentId, Depth)
(
Select ID,Name,ParentId, 1
FROM MyTable
Union All
Select C.Id, C.Name, t.ParentId, c.Depth +1
FROM @tmp t
INNER JOIN TableCTE C on t.Id = c.ParentId
-- Where t.ParentId IS Not Null
)
SELECT Id, Name, ParentId
FROM TableCTE
回答3:
;WITH cte AS
(
SELECT A.ID
,A.ParentID
,A.NAME
,A.DEPTH
FROM @tmp A
WHERE A.ParentID IS NULL
UNION ALL
SELECT B.ID
,B.ParentID
,B.NAME
,B.DEPTH
FROM cte A
INNER JOIN
@tmp B on B.ParentID = A.ID
WHERE B.ParentID IS NOT NULL
)
SELECT * FROM cte
来源：https://stackoverflow.com/questions/8483879/how-to-get-the-full-hierarchy-with-sql-cte