分班问题

app/models/course.rb

@@ -146,7 +146,7 @@ class Course < ApplicationRecord
   def teacher_group(user_id)
     data =
       if teacher_course_groups.exists?(user_id: user_id)
-        teacher_course_groups.joins(:course_group).where(user_id: user_id)
+        teacher_course_groups.joins(:course_group).where(user_id: user_id).distinct
           .pluck('course_groups.id', 'course_groups.name')
       else
         course_groups.pluck(:id, :name)