mysql 分组取最新的一条记录(整条记录)

有没有办法让 group by 执行前分组？有的 ，子查询！sql

最简单的 ：post

SELECT * FROM (SELECT * FROM posts ORDER BY dateline DESC) GROUP BY  tid ORDER BY dateline DESC LIMIT 10

eg:元宝余额查询
条件：要根据acct_id分组，找出最近的一条记录，并根据newyuanbao降序排序。
"SELECT acct_id,newyuanbao FROM (SELECT acct_id,newyuanbao FROM chongzhi_ok ORDER BY `timestamp` DESC) A GROUP BY  A.acct_id ORDER BY A.newyuanbao+0 DESC LIMIT 100";