这能查出所有010399下面的子级，你再做个过滤把010399，010398那条去掉

WITH TABLE1 AS (

SELECT '010399' AS GRADE1 , '010398' AS GRADE2 FROM DUAL UNION ALL

SELECT '010398' AS GRADE1 , '010302' AS GRADE2 FROM DUAL UNION ALL

SELECT '010398' AS GRADE1 , '010303' AS GRADE2 FROM DUAL UNION ALL

SELECT '010398' AS GRADE1 , '010304' AS GRADE2 FROM DUAL UNION ALL

SELECT '010199' AS GRADE1 , '010198' AS GRADE2 FROM DUAL UNION ALL

SELECT '010199' AS GRADE1 , '010298' AS GRADE2 FROM DUAL UNION ALL

SELECT '010198' AS GRADE1 , '010101' AS GRADE2 FROM DUAL UNION ALL

SELECT '010198' AS GRADE1 , '010201' AS GRADE2 FROM DUAL UNION ALL

SELECT '019998' AS GRADE1 , '010199' AS GRADE2 FROM DUAL

)

SELECT

*

FROM

TABLE1

START WITH

GRADE1 = '010399' -- 参数

CONNECT BY

PRIOR GRADE2 = GRADE1

with  tmp as (

select '010399' as parent_id,'010398' as sub_id from dual union all

select '010398' as parent_id,'010302' as sub_id from dual union all

select '010398' as parent_id,'010303' as sub_id from dual union all

select '010398' as parent_id,'010304' as sub_id from dual union all

select '010199' as parent_id,'010198' as sub_id from dual union all

select '010199' as parent_id,'010288' as sub_id from dual ) 

select 

a.parent_id,

b.sub_id

 from tmp a,

 tmp b 

 where a.parent_id='010399'

 and a.sub_id=b.parent_id