过滤结果日期最大值时

Question

有人可以就这里的错误提出建议吗？

我正在尝试选择一个充满结果的表，有些是重复的，但时间戳不同，所以我想过滤掉最新的日期。

我正在使用以下sql查询，但它只是不断抛出错误？

$sql = "(SELECT  *
FROM    measrate
WHERE TRANS_TIME = (SELECT MAX(TRANS_TIME) FROM measrate)";

Answer 1

sql = "(SELECT  * FROM    measrate WHERE TRANS_TIME = (SELECT MAX(TRANS_TIME) FROM measrate))";

忘了最后一个支架

Answer 2

首先，初始括号应该是不必要的：

SELECT m.*
FROM measrate m
WHERE TRANS_TIME = (SELECT MAX(TRANS_TIME) FROM measrate m2);

其次，如果您只想要某个组的最长时间 - 比如基于列result - 那么将其修改为相关子查询：

SELECT m.*
FROM measrate m
WHERE TRANS_TIME = (SELECT MAX(TRANS_TIME) FROM measrate m2 WHERE m2.result= m.result);