调整

app/controllers/courses_controller.rb

@@ -1498,7 +1498,8 @@ class CoursesController < ApplicationController
                       WHERE cm.role = 4 and
                       (concat(users.lastname, users.firstname) like '%#{search}%' or ue.student_id like '%#{search}%')}
     elsif group_id.present?
-      sql_select += %Q{ WHERE cm.role = 4 and cm.course_id = #{@course.id} and cm.course_group_id = #{group_id}}
+      group_id = group_id.is_a?(Array) ? group_id.map(&:to_i) : [group_id.to_i]
+      sql_select += %Q{ WHERE cm.role = 4 and cm.course_id = #{@course.id} and cm.course_group_id in (#{group_id.join(",")})}
     else
       sql_select += %Q{ WHERE cm.role = 4 and cm.course_id = #{@course.id}}
     end