利用组函数得出最后创建的记录

select mg.* from member_gold mg 

left JOIN
(
select DISTINCT(mg.memberid), MAX(mg.createtime) createtime  from member_gold mg group by mg.memberid order by mg.createtime  desc
) mgresult 

on mgresult.memberid = mg.memberid

where 1=1 
and mg.createtime = mgresult.createtime