如何查找某个对象的定义（V$_X$_DBA）[6]

dept                                     deptno                                   number(22)
dept                                     dname                                    varchar2(14)
dept                                     loc                                      varchar2(13)
dummy                                    dummy                                    number(22)
emp                                      empno                                    number(22)
emp                                      ename                                    varchar2(10)
emp                                      job                                      varchar2(9)
emp                                      mgr                                      number(22)
emp                                      hiredate                                 date(7)
emp                                      sal                                      number(22)