Question

我的表结构是（id，cluster，qid，priority）。我试图找出如何显示每个群集的最大优先级值。假设群集1的优先级为100,102,105。我想显示包含105的记录。请帮助。

Answer 1

这篇文章解释了如何为每个组选择具有最大值的行。

http://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/

Answer 2

select cluster, MAX(priority) from structure group by cluster;

查找所有列TRY

select *  from structure
where priority = (
                select MAX(priority) from structure as s 
                where s.cluster = structure.cluster
              );

Answer 3

您可以使用内部联接筛选出行，例如：

select  s.*
from    structure s
join    (
        select  cluster, MAX(priority) maxprio
        from    structure 
        group by 
                cluster
        ) filter
on      s.cluster = filter.cluster
        and s.priority = filter.maxprio

如果它们都具有该群集的最大优先级，则会返回多行。

分组依据和最大的MySQL查询问题

3 个答案: