sql="select users.*,sum(IFNULL(0,student_works.final_score))/#{homework_count} score from student_works left outer join users on student_works.user_id = users.id"<<
" where homework_common_id in ( select id from homework_commons where homework_commons.course_id = #{course.id}) GROUP BY student_works.user_id ORDER BY score limit 0,6"
sql="select users.*,sum(IFNULL(0,student_works.final_score))/#{homework_count} score from student_works left outer join users on student_works.user_id = users.id"<<
" where homework_common_id in ( select id from homework_commons where homework_commons.course_id = #{course.id}) GROUP BY student_works.user_id ORDER BY score limit 0,4"
better_students=User.find_by_sql(sql)
# 找出在课程讨论区发帖回帖数最多的
active_students=[]
sql1=" select users.*,count(author_id) active_count from messages "<<
" LEFT JOIN users on messages.author_id = users.id "<<
" where messages.board_id in (select id from boards where boards.course_id = #{course.id} ) "<<
" GROUP BY messages.author_id ORDER BY count(author_id) desc "<<