my $sth = $dbh->prepare('
   SELECT *
     FROM post_translations
     JOIN posts
       ON post_translations.post_translation_id = posts.post_translation_id
     JOIN languages
       ON post_translations.lang_id = languages.lang_id
    WHERE posts.post_id = ?
      AND languages.lang_name = ?
');

$sth->execute($post_id, $language_name);