오라클 티베로 계층쿼리 정렬

SELECT department_id, LPAD(' ' , 3 * (LEVEL-1)) || department_name, LEVEL
      FROM departments
     START WITH parent_id IS NULL
     CONNECT BY PRIOR department_id  = parent_id
    ORDER SIBLINGS BY department_name;

부분을 필요로 할 때는 

SELECT department_id, LPAD(' ' , 3 * (LEVEL-1)) || department_name, LEVEL
      FROM departments
     START WITH 컬럼명 = 초기값
     CONNECT BY PRIOR department_id  = parent_id