Question

考虑到我有下表

WindDirection | WindSpeed | Date
            W |       12  | 17/01/14
          NNW |       20  | 20/02/14
           SE |       15  | 30/04/14
          ENE |       25  | 21/06/15
          NNE |       23  | 10/12/15
          WSW |       8   | 07/01/15
            S |       19  | 05/06/15

我如何获得每年的最高金额？我想要实现这个

Year | WindSpeed | WindDirection
2014 |        20 |           NNW
2015 |        25 |           ENE

这是我的查询，它不起作用，只是让你有了一个想法

SELECT CONCAT("20", SUBSTRING(`Date`, -2)) AS `Year`, `WindSpeed`, `WindDirection`
FROM `weather`
WHERE `WindSpeed` = (SELECT MAX(`WindSpeed`) 
                     FROM `weather`)
GROUP BY `Year` DESC

提前致谢！

Answer 1

你很亲密。有多种方法可以执行此操作，但对查询的简单修订是使用相关子查询：

SELECT CONCAT('20', RIGHT(`Date`, 2)) AS `Year`, `WindSpeed`, 
`WindDirection`
FROM `weather` w
WHERE w.WindSpeed = (SELECT MAX(w2.WindSpeed) 
                     FROM weather w2
                     WHERE RIGHT(w2.`Date`, 2) = RIGHT(w.`Date`, 2)
                    )
GROUP BY `Year` DESC;

注意：您似乎将日期存储为字符串。您不应该这样做，因为MySQL提供了正确的日期/日期时间数据类型。如果它存储为date，请使用year()函数而不是字符串操作。

Answer 2

您可以使用以下查询

SELECT  B.Year ,
    WindSpeed ,
    A.WindDirection
FROM    weather A
    INNER JOIN ( SELECT YEAR ,
                        MAX(WindSpeed) AS WindSpeed
                 FROM   ( SELECT    YEAR(Date) AS YEAR ,
                                    WindSpeed ,
                                    WindDirection
                          FROM      weather
                        ) A
                 GROUP BY YEAR
               ) b ON A.WindSpeed = b.WindSpeed
                      AND B.YEAR = YEAR(A.Date)

选择按年分组的最大值

2 个答案: