Using cursor to update column, is this inefficient or illegal?

Question

I have declared a cursor as follows in a PL/SQL procedure:
     cursor C is SELECT a FROM t
FOR UPDATE;
Later on in the procedure, I've written the following:
update t
set b = 'text'
where current of C;
My question is, am I allowed to do this when the column I am updating is not the one which I have selected in the cursor? If this is indeed legal, are there any performance issues involved?
Thanks,
Peter

Answer 1

Peter,
As it is confirmed by our folks that it is LEGAL to update columns that are not
fetched in the CURSOR, I am just going to talk about other things.
CURSOR is a read only resultset in PL/SQL which just gives you a handle to each of the rows that you are fetching from one or more table(s), based on the columns that you select in CURSOR. It is advised that you select the ID columns of the table(s) like PK if available from those tables so that you would not run into updating rows more than what is actually required. If we are not fetching the rows based on UNIQUE value and we use these values in UPDATE statements inside, we may get into trouble. Alternative and proves very good with performance is ROWID. I have used ROWID in CURSOR fetches and it works great.DECLARE
   CURSOR empCur IS
   SELECT ROWID unique_col, ename, job, sal FROM EMP
   WHERE sal > 1000;
BEGIN
   FOR empRec IN empCUR
   LOOP
      UPDATE emp SET job = 'Tech Lead'
      WHERE ROWID = empRec.unique_col;
   END LOOP;
END;Andrew,
Just curious, could you educate me on MVP status from Brainbech?
Thx,
SriDHAR