Oracle 递归函数与等级

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

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;