I want sql query for this output

Question

hi guys
could u tell how can i write sql query for this out put
i have one table like this
ID ACCOUTID TAX
1 1 A
2 1 B
3 2 C
4 2 D
5 3 E
7 NULL F
8 NULL G
MY OUT PUT MUST BE LIKE THIS
ID AID TAX
2 1 A
4 2 D
7 NULL F
8 NULL G
HERE IN THIS OUTPUT I SHOULD HAVE
MAXIMAM ID VALUE FOR A REPEATED AID VALUES
AND
THE ROWS AID VALUES IS NULL ALSO MUST PAPULATED IN THE OUTPUT.
I KNOW ONE SOLUTION LIKE THIS
SELECT MAX(ID),AID,TAX
FROM TABLE T
GROUP BY AID,TAX
UNION ALL
SELECT ID, AIC,TAX
FROM TABLE T
WHERE AID IS NULL;
BUT I WANT SAME RESULT WITH OUT USING LOGICAL OPERATORS.
COULD U PLZ TELL A SOL.

Answer 1

Will this help:
SQL> with t as
  2    (
  3      select 1 ID, 1 ACCOUTID, 'A' TAX from dual union all
  4      select 2, 1, 'B' from dual union all
  5      select 3, 2, 'C' from dual union all
  6      select 4, 2, 'D' from dual union all
  7      select 5, 3, 'E' from dual union all
  8      select 7, NULL, 'F' from dual union all
  9      select 8, NULL, 'G' from dual
10    )
11  --
12  select id, ACCOUTID AID, Tax
13  from
14  (
15    select t.*
16          ,count(1)       over (partition by t.ACCOUTID) cn
17          ,row_number()   over (partition by t.ACCOUTID order by id desc) rn
18    from t
19  )
20  where cn > 1
21  and (rn = 1 or ACCOUTID is null)
22  /
        ID        AID T
         2          1 B
         4          2 D
         8            G
         7            F
-- If I leave out the OR condition then you'll get this:
SQL> ed
Wrote file afiedt.buf
  1  with t as
  2    (
  3      select 1 ID, 1 ACCOUTID, 'A' TAX from dual union all
  4      select 2, 1, 'B' from dual union all
  5      select 3, 2, 'C' from dual union all
  6      select 4, 2, 'D' from dual union all
  7      select 5, 3, 'E' from dual union all
  8      select 7, NULL, 'F' from dual union all
  9      select 8, NULL, 'G' from dual
10    )
11  --
12  select id, ACCOUTID AID, Tax
13  from
14  (
15    select t.*
16          ,count(1)       over (partition by t.ACCOUTID) cn
17          ,row_number()   over (partition by t.ACCOUTID order by id desc) rn
18    from t
19  )
20  where cn > 1
21* and rn = 1
SQL> /
        ID        AID T
         2          1 B
         4          2 D
         8            G
--which follows the description you've given, but not the output