Question

我有下表名为'ArchiveTable'：

+---------+-----------------+---------+-----------------+--------------+------------------+
| maxtemp | maxtemptime     | mintemp | mintemptime     | minwindchill | minwindchilltime |
+---------+-----------------+---------+-----------------+--------------+------------------+
| 27.9    | 3/17/2015 16:55 | 25.8    | 3/17/2015 19:00 | 25.8         | 3/17/2015 19:00  |
+---------+-----------------+---------+-----------------+--------------+------------------+
| 25.7    | 3/17/2015 19:05 | 19.3    | 3/18/2015 9:05  | 19.3         | 3/18/2015 9:05   |
+---------+-----------------+---------+-----------------+--------------+------------------+
| 23.1    | 3/18/2015 19:05 | 18.7    | 3/19/2015 6:30  | 18.7         | 3/19/2015 6:30   |
+---------+-----------------+---------+-----------------+--------------+------------------+

我必须选择'maxtemp'的最大值及其对应的'maxtemptime'日期，'mintemp'的最小值及其对应的日期，以及'minwindchill'的最小值及其对应的日期。

我知道如何使用MAX()和MIN()函数获取最大值和最小值，但我无法将这些值与相应的日期相关联。

Answer 1

请参阅此MySQL Handling of GROUP BY

如果我理解正确你应该做这样的事情

SELECT field1, field2, fieldN, COUNT(field1) AS alias FROM table
  GROUP BY field1
 HAVING maxtemp  = MAX(maxtemp); -- I think this is not correct

虽然我对这个解决方案不是100％肯定你也可以试试这个

SELECT field1, field2, fieldN, COUNT(field1) AS alias FROM table
  GROUP BY field1
 HAVING maxtemp  = (SELECT MAX(maxtemp) FROM table);

Answer 2

如果您可以在不同的行上获取值，那么您可以执行以下操作：

(select a.* from archivetable order by maxtemp limit 1) union
(select a.* from archivetable order by maxtemp desc limit 1) union
. . .

否则，如果您可以这样做：

select atmint.mintemp, atmint.mintempdate,
       atmaxt.maxtemp, atmaxt.maxtempdate,
       atminwc.minwindchill, atminwc.minwindchilldate
from (select min(mintemp) as mintemp, max(maxtemp) as maxtemp, min(minwindchill) as minwindchill
      from archivetable
     ) a join
     archivetable atmint
     on atmint.mintemp = a.mintemp join
     archivetable atmaxt
     on atmaxt.maxtemp = a.maxtemp join
     archivetable atminwc
     on atminwc.minwindchill = a.minwindchill
limit 1;

limit 1是因为多行可能具有相同的值。如果是这样，你可以根据问题的表达方式任意选择其中一个。

从MySQL中选择行并分组使用MAX和MIN

2 个答案: