How to lock a row before update using UPDATE statement ?

Question

I want to lock a row before updating using the UPDATE statement! is there any "reserved word" that I can append to an update statement so, that the row get locked!, also, will the lock gets released automatically once the update is done or do I have to explicitly release the lock?
how can I do this ?
any help is greatly appreciated.
Thanks,
Srini.

Answer 1

For detail information, see http://otn.oracle.com/doc/server.815/a67779/ch4l.htm#10900
The lock will be released by "commit".
FOR UPDATE Examples
The following statement locks rows in the EMP table with clerks located in New York and locks rows in the DEPT table with departments in New York that have clerks:
SELECT empno, sal, comm
FROM emp, dept
WHERE job = 'CLERK'
AND emp.deptno = dept.deptno
AND loc = 'NEW YORK'
FOR UPDATE;
The following statement locks only those rows in the EMP table with clerks located in New York. No rows are locked in the DEPT table:
SELECT empno, sal, comm
FROM emp, dept
WHERE job = 'CLERK'
AND emp.deptno = dept.deptno
AND loc = 'NEW YORK'
FOR UPDATE OF emp.sal;