SQL>SELECT LPAD(' ', 4*(LEVEL-1)) || ename ename, empno, mgr, job
        FROM emp
        START WITH EMPNO=7839
        CONNECT BY PRIOR empno=mgr;
ENAME                     EMPNO        MGR JOB
-------------------- ---------- ---------- ---------
KING                         7839                            PRESIDENT
    JONES                  7566          7839           MANAGER
        SCOTT              7788          7566          ANALYST
            ADAMS          7876          7788          CLERK
        FORD               7902         7566           ANALYST
            SMITH          7369          7902           CLERK

계층구조 쿼리 입니다. 강좌검색해서 계층구조로 보시면 더 자세한 내용 있을꺼에요