mysql中怎样实现排行

mysql中实现排行的办法：使用demo函数，语法为【SELECT banji,avg(score) as AvgS FROM table_test GROUP BY banji ORDER BY AvgS DESC】。

mysql中实现排行的办法：

可用Demo实现

留意里面的A，属于嵌套查询，所以排行会准确。

FROM
(
     SELECT A.*,@rank:=@rank+1 as pm
     FROM 
     (
      SELECT banji,avg(score) as AvgS FROM table_test GROUP BY banji  ORDER BY AvgS   DESC
     ) A ,(SELECT @rank:=0) B
) M
ORDER BY M.banji

假如里面没有子查询，使用下面的SQL，那么排序会出错。出错的取决于GROUP BY 可否有多于一条的分组。

SELECT banji,avg(score) as AvgS ,@rank:=@rank+1 as pm
FROM table_test A,(SELECT @rank:=0) B
GROUP BY banji
ORDER BY AvgS   DESC

缘由：@rank排行发生在GROUP BY 此前。GROUP BY 是对排行后的结果停止分组。假如想对分组后的结果停止排行，请使用子查询。