delete uc from user_certificate uc left join user u on u.userId = uc.userId where u.userId is null;
delete uc from user_course uc left join user u on u.userId = uc.userId where u.userId is null;
delete p from purchase p left join user u on u.userId = p.userId where u.userId is null;
delete pp from purchase_product pp left join purchase p on p.purchaseId = pp.purchaseId where p.purchaseId is null;
delete rg from requirementGroup rg left join user_certificate uc on uc.user_certificateId = rg.user_certificateId where rg.user_certificateId is not null and uc.user_certificateId is null;
delete rg from requirementGroup rg left join user u on u.userId = rg.userId where u.userId is null;
delete r from requirement r left join requirementGroup rg on rg.requirementGroupId = r.requirementGroupId where rg.requirementGroupId is null;
delete cr from courseRequirement cr left join requirement r on r.requirementId = cr.requirementId and r.type = 'Course' where r.requirementId is null;
delete pr from proctorRequirement pr left join requirement r on r.requirementId = pr.requirementId and r.type = 'Proctor' where r.requirementId is null;
delete ur from uploadRequirement ur left join requirement r on r.requirementId = ur.requirementId and r.type = 'Upload' where r.requirementId is null;
delete rgr from requirementGroupRequirement rgr left join requirement r on r.requirementId = rgr.requirementId and r.type = 'RequirementGroup' where r.requirementId is null;