GROUP BY 语句用于结合聚合函数,根据一个或多个列对结果集进行分组
GROUP BY 语法
SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;
例句:
每个学生的总分数
select S,sum(score) sum from sc group by S
多表连接
SELECT Websites.name,COUNT(access_log.aid) AS nums FROM access_log LEFT JOIN Websites ON access_log.site_id=Websites.id GROUP BY Websites.name;