mysql5.7先排序后分组mysql5.7之前可以直接先排序后分组 （分组后获取排序第⼀的数据）
SELECT * FROM
( SELECT * FROM table t上牙外凸
油墨画ORDER BY t.pay_date desc
) x
GROUP BY x.payment_id
5.7版本的mysql在执⾏这条sql语句的时候缺少了⼀个derived的操作，
mysql5.7对⼦查询进⾏了优化，认为⼦查询中的order by可以进⾏忽略，
只要Derived table⾥不包含如下条件就可以进⾏优化：
①、UNION clau
②、GROUP BY
开国大典电影③、DISTINCT
④、Aggregation
⑤、LIMIT or OFFSET
常数项是什么SELECT * FROM
( SELECT * FROM table pp
赞美教师的诗句ORDER BY pp.pay_date desc
LIMIT 10000
风娃娃
保留歌词) x
属牛和属龙GROUP BY x.payment_id
SELECT * FROM
( SELECT * FROM table pp
GROUP BY pp.id
ORDER BY pp.pay_date desc
) x
GROUP BY x.payment_id
SELECT * FROM
( SELECT DISTINCT * FROM table pp
ORDER BY pp.pay_date desc
) x
GROUP BY x.payment_id;
