MySQL取值问题，一表格有重覆产品数据，只单取1笔值

Question

如题，一表格会重覆很多次相同的产品值 product_id
但我每个值只取1个
情况1：取每笔数值时间为最新的1笔

情况2：我指定一个时间范围，在范围中取最新的1笔

请问SQL的语法如何实现呢？ 感谢各位！

如下 (注意_，时间精准到秒数_)

Answer 1

如果是查询整条数据可以用一下sql

情况一：

 SELECT * FROM `tablename` t1 
RIGHT JOIN 
    (SELECT t.`product_id` AS product_id ,MAX(t.`Updatedate`) AS Updatedate 
    FROM `tablename` t 
    GROUP BY t.`product_id`) t2
ON t1.`product_id` = t2.`product_id` AND t1.`Updatedate` = t2.`Updatedate`;

情况2：

 SELECT * FROM `tablename` t1 
RIGHT JOIN 
    (SELECT t.`product_id` AS product_id ,MAX(t.`Updatedate`) AS Updatedate 
    FROM `tablename` t 
    WHERE t.`Updatedate` >'2018-06-07' AND t.`Updatedate`<'2018-06-09'
    GROUP BY t.`product_id`) t2
ON t1.`product_id` = t2.`product_id` AND t1.`Updatedate` = t2.`Updatedate`;