oracle 树

 SELECT     t1.bill_id,   t1.item_code_father,
                t1.material_code_father,
                t1.technic_status_father,
                t1.item_code_child,
                t1.material_code_child,
                t1.technic_status_child,
                 ROUND(sf_gettotal_qty(SYS_CONNECT_BY_PATH(t1.qty /
                                                           NVL(t1.factor, 1),
                                                           '*')),
                       8) qty,
                 t1.assembly1_code
            FROM edm_bom t1 JOIN edm_materiel_edition t2 ON t1.item_code_child = t2.item_innercode JOIN edm_master t3 ON t2.item_id = t3.item_id
           WHERE t1.assembly1_code is not null and --装配路线不为空
                 t3.PDM_CLASS <> '13' and --不为整入散发件
                 (t3.p_m = '采购' or t3.PDM_CLASS = '10' or
                 t3.PDM_CLASS = '11' or PRIOR t3.PDM_CLASS = '13' --采购件,半成品，零合件，整入散发件的子件
                 ) 
           START WITH t1.item_code_father ='EQ2050F' /* AND
                      t1.item_code_father  NOT IN  ('610001ZJ-A00','610001ZJ-B00','620001ZJ-A00','620001ZJ-B00')*/
                      AND t1.effect_date <= to_date('20100415','yyyymmdd') AND
                      t1.INVALID_DATE > to_date('20100415','yyyymmdd')
          CONNECT BY nocycle PRIOR t1.item_code_child = t1.item_code_father
                   and t1.item_code_father NOT IN  ('610001ZJ-A00','610001ZJ-B00','620001ZJ-A00','620001ZJ-B00')
                    AND t1.effect_date <= to_date('20100415','yyyymmdd') AND
                     t1.INVALID_DATE > to_date('20100415','yyyymmdd') AND LEVEL < 21;          
这是我错误的代码，我是想对   EQ2050F 下的所有节点进行展开，当遇到父节点为'610001ZJ-A00','610001ZJ-B00','620001ZJ-A00','620001ZJ-B00' 的时候 不向下继续展开；
这个展开的条数不正确，因为 这个展开的条数应该等于    EQ2050F  下所有展开的条数- 以为'610001ZJ-A00','610001ZJ-B00','620001ZJ-A00','620001ZJ-B00'  为父节点展开的条数；是不是我上面的语句写的有问题，请大家帮帮忙看看看应该怎么修改