create table student(
	uid int unsigned primary key not null auto_increment,
	name varchar(50) not null,
	age tinyint unsigned not null,
	sex enum('M','W') not null
);

create table course(
	cid int unsigned primary key not null auto_increment,
	cname varchar(50) not null,
	credit tinyint unsigned not null
);

create TABLE exame(
	uid INT UNSIGNED NOT NULL,
	cid INT UNSIGNED NOT NULL,
	time DATE NOT NULL,
	score FLOAT NOT NULL,
	PRIMARY KEY(uid, cid)
);	

insert into student(name,age,sex) values
('zhang san', 18, 'M'),
('gao yang', 20, 'W'),
('chen wei', 22, 'M'),
('lin feng', 21, 'W'),
('liu xiang', 19, 'W');

insert into course(cname, credit) values
	('C++ jichu', 5),
	('C++ gaoji', 10),
	('C++ xiangmu', 8),
	('C++ algorithm', 12);

insert into exame(uid,cid,time,score) values
(1,1,'2021-04-09',99.0),
(1,2,'2021-04-10',80.0),
(2,2,'2021-04-10',90.0),
(2,3,'2021-04-12',85.0),
(3,1,'2021-04-09',56.0),
(3,2,'2021-04-10',93.0),
(3,3,'2021-04-12',89.0),
(3,4,'2021-04-11',100.0),
(4,4,'2021-04-11',99.0),
(5,2,'2021-04-10',59.0),
(5,3,'2021-04-12',94.0),
(5,4,'2021-04-11',95.0);