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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
我怎麼會在導軌做到這一點:(我試過下面有重大失誤)複雜的聯接查詢軌
category_rs = CourseEnrollment.select("course_categories.title, COUNT(*) as count").
joins(:courses, :course_categories).
group("course_categories.id").
order("course_categories.title")
你準確得到了什麼錯誤? – 2011-03-16 17:09:08