How to summarize ?

Question

Hi all,
i have to develop a oracle sql-statement (no pl/sql) based on 1 table and a conditional sum. I have tried different case statements with group by, but i'm still not able to solve the problem. Any help appreciated.
The Columns:
id, value, flag, time
1, 100, a, 01.01.2005
1, 110, a, 01.02.2005
1, 120, a, 01.04.2005
1, 115, a, 01.04.2005
2, 105, b, 01.01.2005
2, 105, b, 01.02.2005
2, 130, b, 01.04.2005
Each id has only one flag a or b. For each id exists only one value per month.
flag a meens: the value is yet summarized
flag b meens: the value needs to be summarized
The Query:
List each id betwenn 01.01.2005 and 01.04.2005 and the value. For flag "a", take only the value of the last month, wich is 01.04.2005. It must be the last month, because of possible negative values before. For flag "b" summarize the values between 01.01.2005 and 01.04.2005 for each id.
Thanks and Regards,
Hen

Answer 1

If you can use analytic functions, then something like:
SELECT id, value, time
FROM (SELECT id, value, time,
             ROW_NUMBER() OVER (PARTITION BY id,
                                ORDER BY time DESC) rn
      FROM table
      WHERE flag = 'a' and
            time BETWEEN TO_DATE('01.01.2005', 'mm.dd.yyyy') AND
                         TO_DATE('01.04.2005 23:59:59', 'mm.dd.yyyy hh24:mi:ss'))
WHERE rn = 1
UNION ALL
SELECT id, SUM(VALUE), TO_DATE('01.04.2005', 'mm.dd.yyyy')
FROM table
WHERE flag = 'b' and
      time BETWEEN TO_DATE('01.01.2005', 'mm.dd.yyyy') AND
                   TO_DATE('01.04.2005 23:59:59', 'mm.dd.yyyy hh24:mi:ss'))
GROUP BY idIf you cannot use analytics, then something like:
SELECT id, value, time
FROM table o
WHERE flag = 'a' and
      time = (SELECT MAX(time)
              FROM table i
              WHERE o.id = i.id and
                    i.time BETWEEN TO_DATE('01.01.2005', 'mm.dd.yyyy') AND
                                   TO_DATE('01.04.2005 23:59:59', 'mm.dd.yyyy hh24:mi:ss'))
UNION ALL
SELECT id, SUM(VALUE), TO_DATE('01.04.2005', 'mm.dd.yyyy')
FROM table
WHERE flag = 'b' and
      time BETWEEN TO_DATE('01.01.2005', 'mm.dd.yyyy') AND
                   TO_DATE('01.04.2005 23:59:59', 'mm.dd.yyyy hh24:mi:ss'))
GROUP BY idHTH
John