Help with a select statement

Question

I have a table in the folowing format:
date(dd/mm/yyyy) comments(varchar2)
04/09/2007 abcd
04/09/2007 efghij
07/09/2007 klmn
08/09/2007 opqrs
08/09/2007 tuvwxyz
I trying to write a SQL to give me the length of
longest concatenated string of "comments' among the dates.
eg. the query should return : 12 , because date '08/09/2007'
has the longest string when concatenated.
thanks in advance.

Answer 1

I am not sure if the use of the row_number function inside the following query works on 10.1.0.5. If you have troubles, you'd have to nest the row_number analytic function a level deeper.
This one works on 10gR2:
SQL> select max(c) keep (dense_rank last order by length(c)) comments
  2    from ( select mydate
  3                , rn
  4                , c
  5             from mytable
  6            model
  7                  partition by (mydate)
  8                  dimension by (row_number() over (partition by mydate order by comments) rn)
  9                  measures (cast(comments as varchar2(100)) c)
10                  rules
11                  ( c[any] order by rn desc = c[cv()] || c[cv()+1]
12                  )
13         )
14   where rn = 1
15  /
COMMENTS
opqrstuvwxyz
1 rij is geselecteerd.Note that there isn't a column present that decides which comment should be before another comment.
Regards,
Rob.