Oracle 递归函数与等级

--基数数据
1 SELECT  ID, 
        mt.materialtypename,
        mt.parenttypeid   
FROM    material_type mt;

使用递归还是与LEVEL

1 SELECT  ID, 
2         mt.materialtypename,
3         mt.parenttypeid, 
4         SUBSTR(SYS_CONNECT_BY_PATH(mt.materialtypename,'->'),3)   DisplayLevel,
5         level 
6 FROM    material_type mt
7         START   WITH nvl(mt.parenttypeid,0)=0
8         CONNECT BY PRIOR ID=mt.parenttypeid;

CONNECT BY 子句定义表的相互联系

START   WITH 子句定义的开始起点

level 查询深度