mysql 分组topN

 比较快的实现：

select a.* from his_tender_count a join (select trans_month,max(create_time)as create_time from his_tender_count group by trans_month) b on a.trans_month=b.trans_month and a.create_time=b.create_time where a.trans_month> DATE_FORMAT(NOW(),'%Y');

| id   | trans_amount  | trans_count | trans_month | count_date          | create_time         |
+------+---------------+-------------+-------------+---------------------+---------------------+
|    2 | 17.3890614901 |         313 | 2017-02-01  | 2017-07-26 16:19:29 | 2017-07-26 16:19:29 |
|    3 | 24.1876869497 |         290 | 2017-06-01  | 2017-07-26 16:19:29 | 2017-07-26 16:19:29 |