Question

鉴于以下两个表：

用户（user_id，用户名，位置，电子邮件）
投票（user_id，value，date，ip）

如何执行MySQL查询以返回所有用户的总票数和每个用户的投票总数？

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，并非真正必要。所以这是一个外连接版本：

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

这对我有用：

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)

帮助MySQL查询

2 个答案: