emp_id                                                NUMBER(10)
emp_name                                           VARCHAR2(20)

salary                                                  NUMBER(10,2)

可以通过下面的语句查询重复的记录：

SQL> select * from employee;

    EMP_ID EMP_NAME                                  SALARY

---------- ---------------------------------------- ----------

         1 sunshine                                      10000

         1 sunshine                                      10000

         2 semon                                         20000

         2 semon                                         20000

         3 xyz                                           30000

         2 semon                                         20000