oracle建表语句

create table students (
student_id number(5) constraint student_pk primary key,
moniter_id number(5),
name varchar2(10) not null,
sex varchar2(6)
constraint sex_chk check(sex in('男','女')),
job date,
specialty varchar2(10)
);


create table departments (
department_id number(3)
constraint department_pk primary key,
department_name varchar2(8) not null,
address varchar2(40)
);


create table teachers(
teacher_id number(5) 
constraint teacher_pk primary key,
name varchar2(10) not null,
title varchar2(6),
hire date ,
bonus number(7,2),
wage number(7,2),
department_id number(3) 
);


create table student_grade (
student_id number(5),
course_id number(5),
grade number(4,1)
);
alter table student_grade add constraint student_grade_pk primary key (student_id,course_id);


create table grades(
grade_id varchar2(1) constraint grades_pk primary key,
low_score number(4,1),
high_score number(4,1),
grade varchar2(6)

);

ALTER TABLE students RENAME TO students;--修改表名
ALTER TABLE students RENAME COLUMN job TO dob; --修改表列名
ALTER TABLE students MODIFY NAME1 NUMBER(20); --修改字段类型
ALTER TABLE students ADD ADDRESS VARCHAR2(40); --添加表列
ALTER TABLE students DROP(ADDRESS); --删除表列