为约束为的列选择最大值

如何解决为约束为的列选择最大值

| 表如下 公司，垂直，计数 对于每个公司，我想根据具有最高计数的特定行业来获得计数的总和 公司垂直计数 IBM财务10 IBM研发5 IBM PR 2 我想得到以下输出 IBM财务17     

解决方法

        自联接应该做到这一点。

select company,vertical,total_count
from(
    select sum(counts) as total_count
    from table
    )a
cross join table
where counts=(select max(counts) from table);

根据您的RDBMS，您还可以使用窗口函数（例如，sum（count）over（）作为total_count），而不必担心交叉联接。     ,        这与“如何获取MAX行”的问题有所不同（DBA.SE链接） 通过简单的汇总即可获得每个公司的总计和最高垂直 使用这些来标识源表中的行 这样的东西，未经测试

SELECT
    t.Company,t.Vertical,m.CompanyCount
FROM
    ( --get total and highest vertical  per Company
    SELECT
        COUNT(*) AS CompanyCount,MAX(Vertical) AS CompanyMaxVertical,Company
    FROM MyTable
    GROUP BY Company
    ) m
    JOIN --back to get the row for that company with  highest vertical
    MyTable t ON m.Company = t.Company AND m.CompanyMaxVertical = t.Vertical

编辑：这比ROW_NUMBER更接近标准SQL，因为我们不知道平台     ,        

select Company,Vertical,SumCounts
from (       
        select Company,row_number() over(partition by Company order by Counts desc) as rn,sum(Counts) over(partition by Company) as SumCounts
        from YourTable
     ) as T
where rn = 1

    ,        

SELECT company,total_sum
FROM (
    SELECT Company,sum(counts) over (partition by null) as total_sum,rank() over (order by counts desc) as count_rank
    FROM the_table
) t
WHERE count_rank = 1