话说：comments表 ， 其中message_user_id为where条件
其中message_id需要获取messages表中对应id的title
其中user_id需要获取users表中的name
求sql语句
select *,(select title from messages where id=a.message_id) as message_title,(select name from users where user_id=a.message_user_id) as user_name from comments as a where a.message_user_id = xxx;
select message_user_id, messages.title, users.name from comments, messages, users while message_id = messages.id and user_id = users.id and message_user_id = $id
