At 02:31 PM 24/08/2004 -0300, you wrote:

>I am logged as SYSDBA.
>I cannot execute one SQL: "GRANT SELECT (ID,ROTULO) ON TBL_CLIENTES TO
>GUEST"

The SELECT privilege applies to tables.

>But I may execute: "GRANT UPDATE (ID,ROTULO) ON TBL_CLIENTES TO GUEST"

The UPDATE privilege (alone) can be applied to columns.

>Why?

That's the way privileges work. :-)
If you want to prevent your GUEST user from being able to see certain
columns of a table, don't grant SELECT rights to that table: instead,
create a view containing the columns GUEST is allowed to see and grant
SELECT on the view.

./heLen