如何从此表中选择并添加平均值然后排序[重复]

Posted 2023-02-24

【中文标题】如何从此表中选择并添加平均值然后排序[重复]

【英文标题】：how to select from this table and add average value and then sort [duplicate]

【发布时间】：2012-04-24 20:01:45

【问题描述】：

可能重复：how to select, average and sort in mysql table

我在 mySql 中有一张像这张图片一样的表

我想编写一个查询，结果将按 LESSON 列分组，并添加新行，即 LESSON 列的平均值和 CNT 列值的总和....

我使用此查询，但它给出的结果如图 3 所示，在这种情况下我无法按 PERC 排序

select no, STUD_ID,CLASS,LESSON, AVG(PERC) as PERC,SUM(CNT) as CNT from t_lesson where LESSON='CHEM' group by CLASS
union all
select no,STUD_ID,CLASS,'AVERAGE' as LESSON, AVG(PERC) as PERC, SUM(CNT) as CNT from t_lesson where LESSON='CHEM' group by LESSON

【参考方案1】：

select * from <your query> order by PERC

至极：

select * from (

select no, STUD_ID,CLASS,LESSON, AVG(PERC) as PERC,SUM(CNT) as CNT from t_lesson where LESSON='CHEM' group by CLASS
union all
select no,STUD_ID,CLASS,'AVERAGE' as LESSON, AVG(PERC) as PERC, SUM(CNT) as CNT from t_lesson where LESSON='CHEM' group by LESSON

) as sub order by PERC DESC