e1.emp_name=e2.emp_name and e1.salary=e2.salary);

    EMP_ID EMP_NAME                                     SALARY

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

         1 sunshine                                      10000

         3 xyz                                             30000

         2 semon                                         20000

2. 删除的几种方法：

（1）通过建立临时表来实现

SQL>create table temp_emp as (select distinct * from employee) 

SQL> truncate table employee; (清空employee表的数据）

SQL>

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