I tried upgrading the course but got the error message below. I'll try to have the course tables deleted manually. Thanks for your help.
--Hieu
----------------------
WeBWorK error
An error occured while processing your request. For help, please send mail to this site's webmaster (root@localhost), including all of the following information as well as what what you were doing when the error occured.
Mon Jul 31 22:31:10 2017
Warning messages
Error messages
DBD::mysql::db do failed: Incorrect table name '2017_Fall_Discrete_Structures_03160_2_Nguyen_global_user_achievement' at /opt/webwork/webwork2/lib/WeBWorK/DB/Schema/NewSQL/Std.pm line 828.
Call stack
The information below can help locate the source of the problem.
in WeBWorK::DB::Schema::NewSQL::Std::handle_error called at line 299 of /opt/webwork/webwork2/lib/WeBWorK/DB/Schema/NewSQL/Std.pmin WeBWorK::DB::Schema::NewSQL::Std::tableFieldExists called at line 222 of /opt/webwork/webwork2/lib/WeBWorK/Utils/CourseIntegrityCheck.pmin WeBWorK::Utils::CourseIntegrityCheck::checkTableFields called at line 110 of /opt/webwork/webwork2/lib/WeBWorK/Utils/CourseIntegrityCheck.pmin WeBWorK::Utils::CourseIntegrityCheck::checkCourseTables called at line 2402 of /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/CourseAdmin.pmin WeBWorK::ContentGenerator::CourseAdmin::upgrade_course_form called at line 454 of /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/CourseAdmin.pmin WeBWorK::ContentGenerator::CourseAdmin::body called at line 155 of /opt/webwork/webwork2/lib/WeBWorK/Template.pmin WeBWorK::Template::template called at line 531 of /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator.pmin WeBWorK::ContentGenerator::content called at line 380 of /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator/CourseAdmin.pmin WeBWorK::ContentGenerator::CourseAdmin::content called at line 203 of /opt/webwork/webwork2/lib/WeBWorK/ContentGenerator.pmin WeBWorK::ContentGenerator::go called at line 382 of /opt/webwork/webwork2/lib/WeBWorK.pm