I have this ActiveRecord query issue = Issue.find(id) issue.articles.includes(:category).merge(Category.where(permalink: perma)) And the translated to mysql query SELECT `articles`.`id` AS t0_r0, `articles`.`title` AS t0_r1, `articles`.`hypertitle` AS t0_r2, `articles`.`html` AS t0_r3, `articles`.`author` AS t0_r4, `articles`.`published` AS t0_r5, `articles`.`category_id` AS t0_r6, `articles`.`iss