Finding a date with the largest sum

Question

I have a database of transactions, accounts, profit/loss, and date. I need to find the dates which the largest profit occurs by account. I have already found a way to find these actually max/min values but I can't seem to be able to pull the actual date from it. My code so far is like this:

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

Ideally I would like to see account num, the min or max, and then the date which this occurred on.

Answer 1

Try something like this to get the min and max amount for each customer and the date it happened.

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

If you want the data for just this year you could add a where clause to the end of the statement

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

Answer 2

The easiest way to do this is using window/analytic functions. These are ANSI standard and most databases support them (MySQL and Access being two notable exceptions).

Here is one way:

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

The subquery calculates the minimum and maximum amount for each account, using min() as a window function. The outer query selects these values. It then uses conditional aggregation to get the first date when each of those values occurred.

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