SQL recursive query

问题

I have a Table Category,

1) Id
2) CategoryName
3) CategoryMaster

with data as:

1 Computers 0
2 Software 1
3 Multimedia 1
4 Animation 3
5 Health 0
6 Healthsub 5

and i have created recursive query as:

 ;WITH CategoryTree AS
 (
  SELECT *, CAST(NULL AS VARCHAR(50)) AS ParentName, 0 AS Generation    
  FROM dbo.Category    
  WHERE CategoryName = 'Computers'

  UNION ALL        

  SELECT Cat.*,CategoryTree.CategoryName AS ParentName, Generation + 1    
  FROM dbo.Category AS Cat  INNER JOIN 
  CategoryTree ON Cat.CategoryMaster = CategoryTree.Id
 )

 SELECT * FROM CategoryTree

I get the results for parent category to bottom, like i get all sub categories for computer

but i want the results from bottom-up like from Animation to Computers, please can some one suggest me right direction.

Thank you in advance :)

回答1:

Just swap the fields in the join clause:

WITH CategoryTree AS
        (
        SELECT  *, 0 AS Generation    
        FROM    dbo.Category
        WHERE   CategoryName = 'Animation'
        UNION ALL
        SELECT  Cat.*, Generation + 1    
        FROM    CategoryTree
        JOIN    dbo.Category AS Cat
        ON      Cat.Id = CategoryTree.CategoryMaster
        )
SELECT  *
FROM    CategoryTree

来源：https://stackoverflow.com/questions/4690324/sql-recursive-query