[教学]SQL Server从父节点取出所有的子节点，select all child node

[教学]SQL Server从父节点取出所有的子节点，select all child node from parent node

1. DECLARE @ItemCategory TABLE
   
2. (
   
3.     ChildId INT NOT NULL,
   
4.     Name varchar(50) NOT NULL,
   
5.     ParentId int NULL
   
6. )
   
7. 
   
8. INSERT INTO @ItemCategory SELECT 1, 'Toys', null
   
9. INSERT INTO @ItemCategory SELECT 2, 'Computers', null
   
10. INSERT INTO @ItemCategory SELECT 3, 'Consoles', 2
    
11. INSERT INTO @ItemCategory SELECT 4, 'PlayStation 3', 3
    
12. INSERT INTO @ItemCategory SELECT 5, 'Xbox 360', 2
    
13. INSERT INTO @ItemCategory SELECT 6, 'Games', 1
    
14. INSERT INTO @ItemCategory SELECT 7, 'Puzzles', 6
    
15. INSERT INTO @ItemCategory SELECT 8, 'Mens Wear', null
    
16. INSERT INTO @ItemCategory SELECT 9, 'Mens Clothing', 8
    
17. INSERT INTO @ItemCategory SELECT 10, 'Jackets', 9
    
18. INSERT INTO @ItemCategory SELECT 11, 'Rain Coats', 10
    
19. 
    
20. DECLARE @ParentId INT = 1
    
21. 
    
22. ;
    
23. with cte as (
    
24.         select * from @ItemCategory where ParentId = @ParentId
    
25.         union all
    
26.         select T.*
    
27.         from @ItemCategory T
    
28.         inner join cte  on cte.ChildId = T.ParentId
    
29. )
    
30. select *  from cte

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