如何在MySQL中按多列分组并统计匹配行数？

直接使用MySQL的GROUP BY子句结合聚合函数COUNT()即可完成需求，无需依赖应用层（如PHP数组）处理。

基础实现SQL #

SELECT 
    Country,
    Subject,
    Level,
    COUNT(*) AS Count
FROM 
    student
GROUP BY 
    Country, Subject, Level

关键部分说明 #

• GROUP BY Country, Subject, Level：将表中Country、Subject、Level三列值完全相同的记录归为同一分组
• COUNT(*) AS Count：统计每个分组内的记录总数，并将结果列命名为Count

仅显示存在重复的分组 #

如果只需要筛选出重复次数大于1的分组，可添加HAVING子句：

SELECT 
    Country,
    Subject,
    Level,
    COUNT(*) AS Count
FROM 
    student
GROUP BY 
    Country, Subject, Level
HAVING 
    Count > 1

内容的提问来源于stack exchange，提问作者user3541184