帮助MySQL查询

Question

鉴于以下两个表：

1. 用户（user_ID的，用户名，位置， 电子邮件）
2. 票（user_ID的，值，日期，IP）

我如何执行MySQL查询来为每个用户返回总票数和总票数的所有用户？

谢谢。

Answer 1

select u.user_id, 
     (select count(user_id) 
      from votes v 
     where v.user_id = u.user_id) as num_votes, 
     (select sum(value) 
      from votes v 
     where v.user_id = u.user_id) as sum_votes 
    from users u 
# if you want: order by ... 

编辑：子选择不是最优雅的解决方案，而不是真的有必要。因此，这里的外部连接的版本：

select u.user_id, count(v.user_id) as num_votes, sum(v.value) as sum_votes 
    from users u 
    left outer join votes v 
    on u.user_id = v.user_id 
group by u.user_id 

Answer 2

这个工作对我来说：

create table user 
(
    id int not null auto_increment, 
    name varchar(80) not null, 
    location varchar(80) default '', 
    email varchar(80) default '', 
    primary key(id) 
); 

create table vote 
(
    id int not null auto_increment, 
    count int not null, 
    election_date date, 
    user_id int, 
    primary key(id), 
    foreign key(user_id) references user(id) 
); 

select 
user.name, user.email, sum(vote.count) 
from user 
left join 
vote 
on user.id = vote.user_id 
group by (user_id)