展示班级各科成绩demo sql

1、建表

成绩表：

create table if not exists user_count (

   id int(5) primary key auto_increment,
   userid int(2),
   course varchar(5),
   score int(3)
);

insert into user_count values(1,'语文',60,default);
insert into user_count values(1,'数学',30,default);
insert into user_count values(1,'英语',71,default);
insert into user_count values(2,'语文',30,default);
insert into user_count values(2,'数学',60,default);
insert into user_count values(2,'英语',81,default);
insert into user_count values(3,'语文',70,default);
insert into user_count values(3,'数学',80,default);

insert into user_count values(3,'英语',91,default);

学生信息表：

create table if not exists userinfo(
     id int(4) primary key auto_increment,
     name varchar(10),
     tel varchar(11)
) charset utf8;

insert into userinfo values(default,'ldw','1867700');
insert into userinfo values(default,'ch','18632700');
insert into userinfo values(default,'fj','1867322700');

2、关联查询

select us.id 学号,us.name 姓名,
       sum( case uc.course when '语文' then uc.score else 0 end) as 语文,
       sum( case uc.course when '数学' then uc.score else 0 end) as 数学,
       sum( case uc.course when '英语' then uc.score else 0 end) as 英语,
       sum(uc.score) as 总分
       from user_count uc
left outer join userinfo us on us.id = uc.userid

group by us.id,us.name order by sum(uc.score) desc;