Question

我在SQL中有一个查询：

 select fldCustomer, fldTerminal, COUNT(fldbill)
 from tblDataBills
 group by fldCustomer, fldTerminal
 order by fldCustomer

结果如下：

 fldCustomer    fldTerminal (number of bills)
 0  1   19086
 0  2   10
 0  5   236
 1  1   472
 1  5   3
 1  500 19
 2  1   292
 2  500 22

如何获得每位客户的MAX计数，以便得到像

这样的结果

 0 1 19086
 1 1 472
 2 1 292

提前致谢！

Answer 1

将子查询与row_number()：

一起使用

select fldCustomer, fldTerminal, cnt
from (select fldCustomer, fldTerminal, COUNT(*) as cnt,
             row_number() over (partition by fldCustomer order by count(*) desc) as seqnum
      from tblDataBills
      group by fldCustomer, fldTerminal
     ) db
where seqnum = 1
order by fldCustomer ;

请注意，如果出现关联，则会随意返回其中一行。如果您想要所有这些内容，请使用rank()或dense_rank()。

Answer 2

这可能需要RANK()函数

的一些小技巧


SELECT fldCustomer, fldTerminal, [(number of bills)]
FROM (
    SELECT fldCustomer, fldTerminal, COUNT(fldbill) [(number of bills)],
        RANK() OVER (PARTITION BY fldCustomer ORDER BY COUNT(fldbill) DESC) Ranking
    FROM tblDataBills
    GROUP BY fldCustomer, fldTerminal
) a
WHERE Ranking = 1

通过查询获取组中每条记录的MAX值

2 个答案: