解决空数据库问题

db/migrate/20160511055221_merge_two_homeworks.rb

@@ -6,13 +6,17 @@ class MergeTwoHomeworks < ActiveRecord::Migration
         work.update_column('homework_common_id', 3463)
       end
     end
-    homework = HomeworkCommon.find 3387
-    homework.destroy if homework
-    stu_works = StudentWork.where("homework_common_id = 3387")
-    stu_work_ids = stu_works.empty? ? "(-1)" : "(" + stu_works.map{|work| work.id}.join(',') + ")"
-    stu_work_tests = StudentWorkTest.where("student_work_id in #{stu_work_ids}")
-    stu_work_tests.destroy_all if stu_work_tests
-    stu_works.destroy_all if stu_works
+    begin
+      homework = HomeworkCommon.find 3387
+      homework.destroy if homework
+      stu_works = StudentWork.where("homework_common_id = 3387")
+      stu_work_ids = stu_works.empty? ? "(-1)" : "(" + stu_works.map{|work| work.id}.join(',') + ")"
+      stu_work_tests = StudentWorkTest.where("student_work_id in #{stu_work_ids}")
+      stu_work_tests.destroy_all if stu_work_tests
+      stu_works.destroy_all if stu_works
+    rescue Exception => e
+      puts e
+    end
   end
 
   def down