How to connect Many to Many correctly?

Question

MySQL

Tell me how to link three tables so that there is something like this output
username: group1, group2, group3, ...

users:

• id
  
• username
  

groups:

• id
  
• title
  

users_groups:

• id
  
• user_id
  
• groups_id
  

Answer 1

SELECT
 CONCAT((SELECT u.`username` FROM `users` u WHERE u.`id` = t.`user_id`), ': ', t.`_groups`)
FROM (
 SELECT 
  ug.`user_id`, GROUP_CONCAT(g.`title` SEPARATOR ', ') AS _groups
 FROM `users_groups` ug
 JOIN `groups` g ON g.`id` = ug.`groups_id`
 GROUP BY ug.`user_id`
) t