oracle 修改表名、列名、字段类型、添加列、删除列

create table emp1(
eon number primary key,
vname varchar2(10)
);

rename emp1 to emp2;
alter table emp2 rename to emp3;

alter table emp3 rename column vname to ename;

alter table emp3 add (job varchar2(20));

alter table emp3 modify (ename varchar2(20));

alter table emp3 drop (job);

alter table emp add (dno number);
create table emp4 as select eno, dno, ename, job, salary,birthday from emp;
drop table emp;
rename emp4 to emp;