mysql 第二天 联合主键

create table chengji(学员id tinyint unsigned,科目 varchar(20),成绩 tinyint unsigned,primary key(学员id,科目)
);
insert into chengji values(1,'musql',88),(2,'php',90),(1,'js',77),(2,'mysql',85);
select * from chengji where 学员id=1 and 科目='js';