遍历树形结构

SQL中遍历树形目录的一个自定义函数，返回一个table

这样调用：select * from MaterielTypeTree('','')

-- 查找制定类别下面的一级子类别
CREATE    function  dbo.MaterielTypeTree
(
     @DepotNumber   varchar ( 50 ),
     @TypeNumber   varchar ( 50 )
)

returns   @TreeInfo   table
(
    TypeNumber  varchar ( 50 )  not   null ,
    TypeName  varchar ( 50 )  not   null ,
    FatherNumber  varchar ( 50 ),
    ELevel  int   not   null  
)
AS
BEGIN
     declare   @level   as   int

     set   @level = 0

     INSERT   INTO   @TreeInfo   SELECT  TypeNumber,TypeName,FatherNumber, @level   FROM  dbo.MaterielType  where  TypeNumber = @TypeNumber   AND  DepotNumber = @DepotNumber
    
         if (  @@ROWCOUNT   > 0 )  -- 如果改成WHILE则全部查询出来
             BEGIN
                 set   @level = @level + 1

                 INSERT   INTO   @TreeInfo   SELECT  M.TypeNumber,M.TypeName,M.FatherNumber, @level   FROM  MaterielType  AS  M  JOIN   @TreeInfo   AS  T  ON  M.FatherNumber  =  T.TypeNumber  AND  T.ELevel  =   @level - 1   AND  M.DepotNumber = @DepotNumber
             END
                 return
END