group分组统计获取组内根据时间排序后的最大其他字段值

select account, COUNT(*) AS count, MAX(access_time) AS max_time,group_concat(location ORDER BY access_time desc  SEPARATOR '='),
SUBSTRING_INDEX(group_concat(location ORDER BY access_time desc  SEPARATOR '='),'=',1) 
 from result_zdr_user_uni   GROUP BY account ORDER BY max_time desc 

核心一：使用group_concat方法获取其他字段。
语法：

group_concat([DISTINCT] 要连接的字段 [Order BY ASC/DESC 排序字段] [Separator '分隔符'])

核心二：使用SUBSTRING_INDEX获取到第一个。