MySQL查询以显示发送方和接收方的名称

Question

I have a table called users which looks like this:

 +----+----------------+
 | id | name           | 
 +----+----------------+
 |  1 | Blake          | 
 |  2 | Jenn           | 
 +----+----------------+

And i have a table called msg which looks like this:

 +----+----------------+----------------+
 | id | sender         | receiver       | 
 +----+----------------+----------------+
 |  1 | 1              | 2              |
 |  2 | 2              | 1              |
 +----+----------------+----------------+

So now i have a problem because i can't figure out how to join msg.sender(id) to users.name(name).

So basicly what i want to end up with, looks kind of like this:

 +----+----------------+----------------+----------------+----------------+
 | id | sender         | sender_name    | receiver       | receiver_name  |
 +----+----------------+----------------+----------------+----------------+
 |  1 | 1              | Blake          | 2              | Jenn           |
 |  2 | 2              | Jenn           | 1              | Blake          |
 +----+----------------+----------------+----------------+----------------+

I hope these illustrations kind of help with what I'm trying to explain.

Answer 1

Just join the users table twice with msg table - Once on sender and then on receiver.

select m.*,
    s.name as sender_name,
    r.name as receiver_name
from msg m
join users s on m.sender = s.id
join users r on m.receiver = r.id;

Answer 2

You should join the user table twice using alias

  select  msg.sender, u1.name  as sender_name, msg.receiver, u2.name as receiver_name
  from msg
  inner join users u1 on u1.id =  msg.sender
  inner join users u2 on u2.id =  msg.receiver