sql练习 -----求出发帖最多的人

最新推荐文章于 2024-12-11 17:48:04 发布

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本文纠正了一种常见的SQL查询错误，即如何正确地找出在文章表中发帖数量最多的作者。通过对比不同写法，解释了为何某些SQL语句无法得出预期结果，并给出了正确的实现方法。

昨天无意识看到同桌的同事在练习sql，其中看到他在写一道题的sql，

求出发帖最多的人？

开始我写的是这句：

select t.authorid,max(total) from (select authorid,count(*) total from articles

group by authorid ) t group by t.authorid 结果去执行，完了，错的！写了两句相当于

写了一句，都是一样的结果。

正确的写法如下：

select teaid,count(*) total from articles group by teaid having count(*) =

(select max(total2) from (select count(*) total2 from articles group by teaid) t);

记得不能写成如下这样哦：

select teaid,count(*) total from articles group by teaid

having total = //total 一定要写成 count(*)

(select max(total2) from (select count(*) total2 from articles group by teaid) t);

下面这样写直接报错
select teaid,count(*) total from articles group by teaid having

count(*)=max(total)

也不应该写成：

select teaid,count(*) total from articles group by teaid

having total = //total 一定要写成 count(*)

(select max(total2) from (select count(*) total2 from articles group by teaid)

as t);//子查询不能加as as只能用作表的别名

下面的写法也会报错

select teaid , count(*) c from articles group by teaid

having count(*) = select max(t.total) from (select teaid,count(*) total from articles group by teaid) t

应该写成下面这样

select teaid , count(*) c from articles group by teaid

having count(*) = (select max(t.total) from (select teaid,count(*) total from

articles group by teaid) t)//应该加上括号