Analytic Functions with GROUP-BY Clause?

Question

I'm just getting acquainted with analytical functions. I like them. I'm having a problem, though. I want to sum up the results, but either I'm running into a limitation or I'm writing the SQL wrong. Any hints for me?
Hypothetical Table SALES consisting of a DAY_ID, PRODUCT_ID, PURCHASER_ID, PURCHASE_PRICE lists all the
Hypothetical Business Question: Product prices can fluctuate over the course of a day. I want to know how much per day I would have made had I sold one each of all my products at their max price for that day. Silly question, I know, but it's the best I could come up with to show the problem.
INSERT INTO SALES VALUES(1,1,1,1.0);
INSERT INTO SALES VALUES(1,1,1,2.0);
INSERT INTO SALES VALUES(1,2,1,3.0);
INSERT INTO SALES VALUES(1,2,1,4.0);
INSERT INTO SALES VALUES(2,1,1,5.0);
INSERT INTO SALES VALUES(2,1,1,6.0);
INSERT INTO SALES VALUES(2,2,1,7.0);
INSERT INTO SALES VALUES(2,2,1,8.0);
COMMIT;
Day 1: Iif I had sold one product 1 at $2 and one product 2 at $4, I would have made 6$.
Day 2: Iif I had sold one product 1 at $6 and one product 2 at $8, I would have made 14$.
The desired result set is:
DAY_ID                 MY_MEASURE
1                        6
1                       14The following SQL gets me tantalizingly close:
SELECT DAY_ID,
  MAX(PURCHASE_PRICE)
  KEEP(DENSE_RANK FIRST ORDER BY PURCHASE_PRICE DESC)
  OVER(PARTITION BY DAY_ID, PRODUCT_ID) AS MY_MEASURE
  FROM SALES
ORDER BY DAY_ID
DAY_ID                 MY_MEASURE
1                      2
1                      2
1                      4
1                      4
2                      6
2                      6
2                      8
2                      8But as you can see, my result set is "longer" than I wanted it to be. I want a single row per DAY_ID. I understand what the analytical functions are doing here, and I acknowledge that I am "not doing it right." I just can't seem to figure out how to make it work.
Trying to do a sum() of max() simply does not work, nor does any semblance of a group-by clause that I can come up with. Unfortunately, as soon as I add the windowing function, I am no longer allowed to use group-by expressions (I think).
I am using a reporting tool, so unfortunately using things like inline views are not an option. I need to be able to define "MY_MEASURE" as something the query tool can apply the SUM() function to in its generated SQL.
(Note: The actual problem is slightly less easy to conceptualize, but solving this conundrum will take me much closer to solving the other.)
I humbly solicit your collective wisdom, oh forum.

Answer 1

Thanks, SY. I went that way originally too. Unfortunately that's no different from what I could get without the RANK function.
SELECT  DAY_ID,
        PRODUCT_ID,
        MAX(PURCHASE_PRICE) MAX_PRICE
  FROM  SALES
  GROUP BY DAY_ID,
           PRODUCT_ID
  ORDER BY DAY_ID,
           PRODUCT_ID
DAY_ID                 PRODUCT_ID             MAX_PRICE             
1                      1                      2                     
1                      2                      4                     
2                      1                      6                     
2                      2                      8