MySQL，通过sql语句创建数据库和表

DROP TABLE if EXISTS userinfo;
CREATE TABLE userinfo(
studentNo int(4) NOT NULL COMMENT '学号',
loginPwd VARCHAR(20) NOT null COMMENT '密码',
studentName VARCHAR(50) NOT NULL COMMENT '学生姓名',
sex CHAR(2) NOT NULL COMMENT '性别',
gradeId INT(4) COMMENT '年级编号',
phone VARCHAR(50) COMMENT '联系电话',
address VARCHAR(255) COMMENT '地址',
bomDate datetime COMMENT '出生时间',
email varchar(50) COMMENT '邮件账号',
identityCard VARCHAR(18) COMMENT '身份证号码',
PRIMARY KEY (studentNo)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

DROP TABLE if EXISTS grade;
CREATE TABLE grade(
gradeId int(4) NOT NULL COMMENT '年级编号',
gradeName VARCHAR(50) NOT null COMMENT '年级名称',
PRIMARY KEY (gradeId)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO userinfo VALUES(1,'123456','张三','男',1901,'12346687','上海','2000-01-01 20:16:23','132464@1231.com','321649816565');
INSERT INTO userinfo VALUES(2,'981566','李四','女',1902,'787373728','北京','2002-05-19 20:16:23','42542@221.com','784534533453');
INSERT INTO userinfo VALUES(3,'321649','王五','女',1903,'453522373','天津','2001-12-13 20:16:23','127822@4537.com','1237434537');
INSERT INTO userinfo VALUES(4,'asdf45','熊大','女',1904,'452722453','重庆','2003-03-08 20:16:23','dsfbdg@163.com','123123738');
INSERT INTO userinfo VALUES(5,'987416','熊二','男',1905,'457834378','绵阳','2000-08-19 20:16:23','adf1sdf34@272.com','45312343453');

INSERT INTO grade VALUES(1901,'软件');
INSERT INTO grade VALUES(1902,'数媒');
INSERT INTO grade VALUES(1903,'道桥');
INSERT INTO grade VALUES(1904,'信安');
INSERT INTO grade VALUES(1905,'AI');

Alter table userinfo add foreign key(gradeId) REFERENCES grade(gradeId);

ALTER TABLE grade CHANGE gradeName grade_name VARCHAR(50);