Unique rows in oracle 11g - oracle

Question

I have a query which returns a set of records as like the one below:-
Date Dept commission
5-Apr Sales 20
4-Apr Sales 21
1-Jan Marketing 35
case 1: If i run a query between 1 Jan and 5 april I should get
Date Dept commission
5 April Sales 76
case 2: and when I run the query between jan 1 and jan 31 should get the output as
Date Dept commission
1 Jan Marketing 35
Case 2 is simple as when i put hte date range getting the required results , but not sure how to handle case 1 to show the max / latest date , the Dept for that date and a sum of the commission for that Dept , date for the selected date range . The output will be a single row with the latest date and department with a sum(commission) for the selected date range.

Answer 1

SELECT
MAX(Date) AS Date
, ( SELECT tt.Dept
FROM tableX tt
WHERE tt.Date = MAX(t.Date)
) AS Dept
, SUM(Commission) AS Commission
FROM
tableX t
WHERE
Date BETWEEN StartDate AND EndDate
The above works in SQL-Server, MySQL, Postgres as the sql-fiddle, test-1 shows, however it does NOT work in Oracle 11g R2 !
This works though (sql-fiddle, test-2):
SELECT
MAX(t.Date) AS Date
, MIN(tt.Dept) AS Dept --- MIN, MAX irrelevant
, SUM(t.Commission) AS Commission
FROM
( SELECT
MAX(Date) AS Date
, SUM(Commission) AS Commission
FROM
tableX
WHERE
Date BETWEEN StartDate AND EndDate
) t
JOIN
tableX tt
ON tt.Date = t.Date
The MIN(tt.Dept) is used to take care of the case you have more than row with the maximum date, say one row with Sales and one with Marketing, both in Apr-5
This works, too, using the LAST_VALUE analytic function (sql-fiddle, test-3):
SELECT
MAX(Date) AS Date
, MIN(Dept) AS Dept
, SUM(Commission) AS Commission
FROM
( SELECT
Date AS Date
, LAST_VALUE(Dept) OVER( ORDER BY Date
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
) AS Dept
, Commission AS Commission
FROM
tableX
WHERE
Date BETWEEN StartDate AND EndDate
) t