Question

我有一个表，其中包含正在使用的两列测试数据：“日期”和“象限”。象限列是一个包含4个可能值（1、2、3或4）的枚举值。

一周中的每一天（具有4个月的日期）具有与之关联的枚举值。

在给定的一天中，该枚举值通常会多次出现。

我正在尝试计算整个表中给定工作日中最常见的象限枚举值。

例如，星期一看到20个枚举值“ 1”和19个值“ 2”。

我只想看看最常见的例子，在此示例中为“ 1”。

类似这样的东西：

Monday.........1
Tuesday........3
Wednesday......4
Thursday.......1
Friday..........2

到目前为止，我已经尝试了以下方法，但它仅提供了象限列每个工作日具有枚举值的总次数。

SELECT DAYNAME(Date) AS Weekday
     , COUNT(quadrant) AS 'Most Likey Damaged Quadrant' 
  FROM damage_tbl 
 WHERE quadrant IS NOT NULL 
 GROUP 
    BY quadrant 
 ORDER
    BY WEEKDAY

以下是指向表和所有右上角数据的链接：https://rextester.com/UQDSB56921

Answer 1

您可以检查this post来查看完成此操作的不同方法（在MySQL中获得argmax）

一种方法（在注释中提到）是自抗联接：

SELECT a.Weekday, a.quadrant FROM (
    SELECT DAYNAME(Date) AS Weekday, quadrant, COUNT(*) AS 'cnt' 
      FROM damage_tbl 
     WHERE quadrant IS NOT NULL 
     GROUP 
        BY WEEKDAY, quadrant
     ORDER
        BY WEEKDAY, count(*) desc ) a LEFT JOIN (
    SELECT DAYNAME(Date) AS Weekday, quadrant, COUNT(*) AS 'cnt' 
      FROM damage_tbl 
     WHERE quadrant IS NOT NULL 
     GROUP 
        BY WEEKDAY, quadrant
     ORDER
        BY WEEKDAY, count(*) desc ) b 
ON a.Weekday = b.Weekday and a.cnt < b.cnt  
WHERE b.Weekday is null

查找给定工作日的最大出现次数

1 个答案: