mysql - 根据一列的最大值选择相同的行，当最大值等于时只选择其中一行

Question

我有一个名为“demo”的表，其中包含以下数据:

Name    Group   MX
A        XY     1
B        YZ     1
B        XY     2
C        YZ     5
C        XY     3
D        YZ     2
E        YZ     1
E        XY     1

I want unique names based on 'MX' maximum value, when the 'MX' for two identical names are equal I need one of them as illustrated below:

Name    Group   MX
A        XY     1
B        XY     2
C        YZ     5
D        YZ     2
E        YZ     1   -- or this {E   XY   1}

This is my query:

SELECT demo.Name, demo.Group, demo.MX
    FROM ( 
        SELECT Name, MAX(MX) AS max_values 
        FROM demo
        GROUP BY Name
     ) demo2
INNER JOIN demo
ON demo.Name = demo2.Name
AND demo.MX = demo2.max_values

它工作得很好，但是当两个名字相同时，它显示如下:

Name    Group   MX
A        XY      1
B        XY      2
C        YZ      5
D        YZ      2
E        YZ      1 
E        XY      1

您推荐哪些方法？

Answer 1

为了避免 Name 和 MX 相等的两个值，您可以使用(假的)聚合函数并按例如分组:

SELECT demo.Name, min(demo.Group), demo.MX
    FROM ( 
        SELECT Name, MAX(MX) AS max_values 
        FROM demo
        GROUP BY Name
     ) demo2
INNER JOIN demo ON demo.Name = demo2.Name AND demo.MX = demo2.max_values
GROUP BY demo.Name, demo.MX