Question

I want to update table with sequence number, I cant create procedure or sequence object so need a update query for this. I have a table with date column, based on minimum date I need to generate a number.

Table Data:-

Date_Value
----------
5th Feb 11
2nd Jan 11
11th Jan 11

After Update :- 
SrNo     Date_Value
------------------- 
1   2nd Jan 11
2   11th Jan 11
3   5th Feb 11

Answer 1

merge into foo
using
(
   select rowid as rid,
          row_number() over (order by date_value) as seqno
   from foo
) t on (foo.rowid = t.rid)
when matched then update
   set srno = t.seqno;

SQLFiddle demo: http://sqlfiddle.com/#!4/d8cc5/2