select ...for update is used in some databases like ORACLE, to
indicate the columns to be updated in a CURSOR:

Ex (I don't remember exactly the sintaxis):

declare
cursor c is
select id,price
from table
where price=50
for update of price

begin
for v_record in c do
begin
insert into table2(id) values (v_record.id);
update table set price=price*2 where current of v_record;
end
end


This example is not too good, because is the same as:

update table set price=price*2 where price=50

but I hope you understand the idea.

In INTERBASE I use DB_KEY to do the same thing. It's very similar.
In some cases I prefere FOR UPDATE, but DB_KEY works good.


Bye,