Specifies update intention on the rows selected by the SELECT statement.
Syntax
FOR UPDATE [ OF [table.]column_name , ...][ NOWAIT ]
Parameters
OF [table.]column_name , ...
Specifies the table's column name to be updated.
NOWAIT
Causes the SELECT statement to return immediately with an error if a lock cannot be acquired on a row in the selection set because of the lock held by some other transaction. The default behavior is for the transaction to wait until it obtains the required lock or until it times out waiting for the lock.
Notes
If you specify FOR UPDATE, the database acquires exclusive locks on all the rows satisfying the SELECT statement. The database does not acquire row level locks if there is an exclusive lock on the table. See the LOCK TABLE statement for information on table locking.
