Help with a MySQL query

Question

Hello guys,

Given the following two tables:

1. users (user_id, username, location, email)
2. votes (user_id, value, date, ip)

How can I perform a MySQL query to return all the users with total number of votes and sum of votes for each user?

Thank you.

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 ...

EDIT: The subselects are not the most elegant solution, and not really necessary. So here's an outer join version:

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

This works for me:

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)