group by查询每组时间最新的一条记录

        select id,userId,userFlag,lontitude,latitude,time,addr,locationdescribe
        from user_position
        group by userId
        having time = max(time)
        and userId in (select id from users where group_code=(select group_code from users where id = #{userId}))
        ORDER BY time desc

--查询出分组的所有按时间降序的记录id并拼接
select group_concat(id order by `time` desc) from user_position group by userId

--查询每个分组中时间最新的那条记录的id
select SUBSTRING_INDEX(group_concat(id order by `time` desc),‘,‘,1) from user_position group by userId

select * from user_position as t 
where t.id in 
(
select SUBSTRING_INDEX(group_concat(id order by `time` desc),‘,‘,1) from user_position 
 group by userId
) 

select * from user_position as t 
where t.id in 
(
select SUBSTRING_INDEX(group_concat(id order by `time` desc),‘,‘,1) from user_position 
 where userId in (select id from users where group_code=(select group_code from users where id = ‘qyid1‘))
 group by userId
) 

select * 
from user_position as u 

select * 
from user_position as u 
group by u.userId 

select * 
from (
select * from user_position order by userId,time desc
) as u 
group by u.userId