Mysql子查询问题

Question

select school_id,count(stu_sex) as scount from stu where (school_id,count(stu_sex)) =(select school_id ,count(stu_sex) as count from stu group by school_id order by count desc limit 1) group by stu_sex;提示: Utilisation invalide de la clause GROUP,这是啥意思？

Answer 1

写这么复杂的sql语句，如果有实际需求而且不影响性能的情况尚可，但是如果性能很差，这样的sql语句必然会被诟病，所以，如果没有实际项目需求，这种sql语句一定要尽量避免，再者，有可能自己都看不懂，扰乱自己的思维。

Answer 2

select school_id,count(stu_sex) as scount 

  from stu 

-- where (school_id,count(stu_sex)) =(select school_id ,count(stu_sex) as count from stu group by school_id order by count desc limit 1) 

group by stu_sex;

把where条件先注释掉，你就发现你写的已经错了，简单查询先写好，再加where条件，还有，两个字段组合的等值写法是没有的，你可以试试用left join

Answer 3

应该是group by的用法是错误的，你这查询太复杂。