复杂的联接查询轨

Question

SELECT course_categories.course_category_title, COUNT(*) as count 
FROM course_enrollments 
JOIN courses ON course_enrollments.course_id = courses.course_id 
JOIN course_categories ON course_categories.id = courses.course_category_id" 
GROUP BY course_categores.id 
ORDER BY courses_categories.title 

我怎么会在导轨做到这一点：（我试过下面有重大失误）

category_rs = CourseEnrollment.select("course_categories.title, COUNT(*) as count"). 
      joins(:courses, :course_categories). 
      group("course_categories.id"). 
      order("course_categories.title") 

Answer 1

我想通了，我需要指定连接为一个字符串。