我有下面这个表格,其中包含以下记录:
create table employee
(
EmpId number,
EmpName varchar2(10),
EmpSSN varchar2(11)
);
insert into employee values(1, 'Jack', '555-55-5555');
insert into employee values (2, 'Joe', '555-56-5555');
insert into employee values (3, 'Fred', '555-57-5555');
insert into employee values (4, 'Mike', '555-58-5555');
insert into employee values (5, 'Cathy', '555-59-5555');
insert into employee values (6, 'Lisa', '555-70-5555');
insert into employee values (1, 'Jack', '555-55-5555');
insert into employee values (4, 'Mike', '555-58-5555');
insert into employee values (5, 'Cathy', '555-59-5555');
insert into employee values (6 ,'Lisa', '555-70-5555');
insert into employee values (5, 'Cathy', '555-59-5555');
insert into employee values (6, 'Lisa', '555-70-5555');
我在这个表中没有任何主键。但是我已经有了上面的记录。 我想删除那些EmpId和EmpSSN字段具有相同值的重复记录。
例如:Emp id 5
如何编写查询以删除这些重复记录?