select / from / where / for

Hi. I have another select statement I don't understand. Can someone explain:

select 'X'
from payroll_transaction_master
where rowid = chartorowid (:ptm_row_id)
for update of ptm_emp_#;

?

Baffled,
Martin Meadows Received on Tue Apr 28 1998 - 00:00:00 CDT