What does the $posts_join filter join to?

posts_join is only a part of the full SQL query, the table you’re joining to is referenced earlier in the query.

You can see the full query with the posts_request filter.

See the documentation for the rest of the query filters.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)