Oracle创建表

---创建一个员工表 **禁止使用or replace
create table emp(
empno number(4),
ename varchar2(10),
job varchar2(9),
mgr number(4),
hiredate date,
sal number(7,2),
comm number(7,2),
deptno number(2)
)
---对字段进行描述 关键字为：comment on column 表.字段 is 描述
comment on column emp.empno is '员工编号';
comment on column emp.ename is '员工姓名';
comment on column emp.job is '员工工作';
comment on column emp.mgr is '员工上级编号';
comment on column emp.hiredate is '员工入职日期';
comment on column emp.sal is '员工薪水';
comment on column emp.comm is '员工补助';
comment on column emp.deptno is '员工部门';

---追加字段 性别 关键字为: alter table 表 add(字段 类型)
alter table emp add(sex varchar2(2));
comment on column emp.sex is '性别';