查找金额最大的日期

Question

我有一个包含交易、账户、损益和日期的数据库。我需要按账户找到最大利润发生的日期。我已经找到了一种方法来查找这些实际的最大/最小值，但我似乎无法从中提取实际日期。到目前为止，我的代码是这样的：

Select accountnum, min(ammount)
from table
where date > '02-Jan-13'
group by accountnum
order by accountnum

理想情况下，我希望看到帐户编号，最小值或最大值，然后是发生这种情况的日期。

Answer 1

尝试这样的事情来获取每个客户的最小和最大金额以及发生日期。

WITH max_amount as (
    SELECT accountnum, max(amount) amount, date
    FROM TABLE
    GROUP BY accountnum, date
),
min_amount as (
    SELECT accountnum, min(amount) amount, date
    FROM TABLE
    GROUP BY accountnum, date
)
SELECT t.accountnum, ma.amount, ma.date, mi.amount, ma.date
FROM table t
JOIN max_amount ma
ON   ma.accountnum = t.accountnum
JOIN min_amount mi
ON   mi.accountnum = t.accountnum

如果你想要今年的数据，你可以在语句的末尾添加一个where子句。

WHERE t.date > '02-Jan-13'

Answer 2

最简单的方法是使用窗口/分析函数。 这些是ANSI标准，大多数数据库都支持它们（MySQL和Access是两个值得注意的例外）。

这是一种方法：

select t.accountnum, min_amount, max_amount,
       min(case when amount = min_amount then date end) as min_amount_date,
       min(case when amount = min_amount then date end) as max_amount_date,
from (Select t.*,
             min(amount) over (partition by accountnum) as min_amount,
             max(amount) over (partition by accountnum) as max_amount
      from table t
      where date > '02-Jan-13'
     ) t
group by accountnum, min_amount, max_amount;
order by accountnum

子查询使用 min() 作为窗口函数计算每个帐户的最小和最大金额。 外部查询选择这些值。 然后，它使用条件聚合来获取每个值发生的第一个日期。

Answer 3

;with cte as
(
  select accountnum, ammount, date, 
  row_number() over (partition by accountnum order by ammount desc) rn,
  max(ammount) over (partition by accountnum) maxamount,
  min(ammount) over (partition by accountnum) minamount
  from table
  where date > '20130102'
)
select accountnum, 
       ammount as amount, 
       date as date_of_max_amount, 
       minamount, 
       maxamount 
from cte where rn = 1