Update while selecting

Question

Is there any way in oracle where we update while selecting.
I have a situation where I select a few rows from a table.
Then I have to update those all those rows witrh some date as sysdate.
I want to make sure that the rows I have selected are only updated and not a single new one.
ex:
select
process something.
update table set filed=sysdate where pk_col in (select --it is the same as 1st select );
but in real time,
when i select 1st time i get 40 rows.
I process them.
now i have to update just those 40 rows,
but this time when I say
update (select --its a second read.... this time select gives me 42 rows)
maybe someone was working and he updated the table and I got 2 more rows.
But as i processed 40, i want to update only 40 rows.
So how can i be sure.
Any ideas. please help.
1 solution is to have a cursor and do the processing and updaing in the cursor.
I process 40 rows and i update only those 40 rows in the cursor.
other way, update when i select. i it possible.
please let me know.
meenakshi

Answer 1

Hi.
Check this please:
CREATE TABLE aux_d
     id NUMBER,
     d_date DATE
INSERT INTO aux_d VALUES(1,null);
INSERT INTO aux_d VALUES(2,null);
INSERT INTO aux_d VALUES(3,null);
COMMIT;
SELECT * FROM aux_d;
ID     D_DATE
1     (null)
2     (null)
3     (null)
UPDATE
  SELECT *
  FROM aux_d
  WHERE id < 3
SET d_date = SYSDATE;
COMMIT;
SELECT * FROM aux_d;
ID     D_DATE
1     14/07/11
2     14/07/11
3     (null)Hope this helps.
Regards.