过滤重复项取时间最近的数据

SELECT * FROM pm_workorder_record_flow a
 WHERE EXISTS (SELECT 1 FROM 
 (SELECT MAX(createddt) sjrq ,machineid
 FROM pm_workorder_record_flow
 GROUP BY machineid)b WHERE a.createddt=b.sjrq AND a.machineid=b.machineid)