MySql Queries

Select the Max Examination Codes from the multiple Codes of group of learners
SELECT application_num, stdid, max_exam, e.* FROM (SELECT g.application_num, stdid, max(a.exam_id) as max_exam FROM osou_gradecard a LEFT JOIN osou_general_info g ON a.stdid=g.app_id WHERE stdid IN (SELECT app_id from osou_general_info WHERE application_num IN ('Enroll1', 'Enroll2', 'Enroll3', 'Enroll4')) GROUP BY stdid) as z LEFT JOIN osou_exam_definitions e ON z.max_exam=e.exam_id