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
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：幼猪
深刻①、UNION clau
②、GROUP BY
③、DISTINCT
山西国税④、Aggregation
龙眼吃多了会上火吗
⑤、LIMIT or OFFSET
SELECT * FROM
( SELECT * FROM table pp
ORDER BY pp.pay_date desc
LIMIT 10000
) x
GROUP BY x.payment_id
SELECT * FROM
帮助他人
( SELECT * FROM table pp
GROUP BY pp.id
七重外壳ORDER BY pp.pay_date desc
) x
GROUP BY x.payment_id
SELECT * FROM
匪夷所思的意思( SELECT DISTINCT * FROM table pp
ORDER BY pp.pay_date desc
) x
我和姨妈GROUP BY x.payment_id;
