没有排序依据的MySQL最大计数

如何解决没有排序依据的MySQL最大计数

| 我有以下MysqL行： SELECT age,count(*) AS total FROM pacient WHERE age BETWEEN 20 AND 40 GROUP BY age ORDER BY age，我需要向其添加一列，仅显示每一行的count（*）的最大值。例如： 13 2 7 18 2 7 23 5 7 24 7 7 26 6 7 32 3 7 38 1 7 41 1 7 46 4 7 这将是3列，第3列显示7，因为7是进行count（*）的第二列中的最高数字。

解决方法

这里的解决方案：

select age,count(*),(select max(c) from 
        (select count(*) as c from pacient where age between 20 and 40 group by age) as x) as t 
from pacient 
where age between 20 and 40 
group by age 
order by age;

, 您是否尝试将查询与另一个查询一起包装？就像是

SELECT A.age,A.total,MAX(A.total) as max_value FROM (
    SELECT age,count(*) AS total 
    FROM pacient
    WHERE age BETWEEN 20 AND 40 
    GROUP BY age ORDER BY age) as A
GROUP BY A.age,A.total

select 
      p.Age,count(*)  CountPerAge,max(ar.AllRecs) AllRecs
   from
      pacient p,( select count(*) AllRecs 
           from pacient p2
           where p2.age between 20 and 40 ) ar
   where 
      p.age between 20 and 40
   group by
      p.age

通过在没有联接条件的情况下联接第二个\“ subselect \”，它将得到笛卡尔结果...由于它是一个没有group by的计数，因此它将始终返回单个记录，因此将联接所有年龄段否则行。该值的MAX（）没问题，因为它是唯一的记录，将按原样返回。 , 使用SQL VIEWS而不是使用子查询总是好事。因为VIEW将具有已编译的结果。

CREATE VIEW subqueryView 
    SELECT age,count(*) AS total 
    FROM pacient
    WHERE age BETWEEN 20 AND 40 
    GROUP BY age ORDER BY age

SELECT A.age,MAX(A.total) as max_value FROM (SELECT FROM subqueryView) as A
GROUP BY A.age,A.total