无限级结构SQL查询所有的下级和所有的下级

/*查找Id为1所有的下级*/
WITH T 
AS(  
    SELECT Id,PId,Name,0 L FROM User WHERE Id=1 
    UNION ALL  
    SELECT U.Id,U.PId,U.Name,L+1    
    FROM User U INNER JOIN T ON U.PId=T.Id   
)  
SELECT * FROM T 

/*查找Id为100所有的上级*/
WITH T 
AS(  
    SELECT Id,PId,Name,0 L FROM User WHERE Id=100 
    UNION ALL  
    SELECT U.Id,U.PId,U.Name,L+1    
    FROM User U INNER JOIN T ON U.Id=T.PId   
)  
SELECT * FROM T