A faster way to combine two SQL table

I would like to give it a try and ask about my codes on here from now on to see if there are improvement for'em

this code is supposed to combine two sql tables into one.

SELECT * FROM (SELECT * FROM posts WHERE id < $lastpost AND position = submitter order by id DESC LIMIT 5) t1 JOIN (SELECT username, firstname, lastname, avatar FROM users) t2 ON t1.submitter = t2.username

I was thinking that there might be a better way doing it using union or anything faster, if I'm even right about what I'm saying.

Assuming that each post has exactly one submitter, this is a more natural formulation of the query.

SELECT posts.*
     , users.username
     , users.firstname
     , users.lastname
     , users.avatar
    FROM posts
        JOIN users
            ON posts.submitter = users.username
    WHERE
        posts.id < $lastpost
        AND posts.position = posts.submitter
    ORDER BY posts.id DESC 
    LIMIT 5

However, its performance is likely to be similar to your original query. To investigate performance issues, run EXPLAIN SELECT to help you verify that the necessary indexes are in place.

StackExchange Code Review Q#47121, answer score: 4