What is the difference between granting privilege directly and via role

Question

When we want create a view in user1 schema , that user must be granted by select privilege on table user2.t2 , but not via a role , what is the difference?
Is there any other privileges that must be directly granted?

Answer 1

please look into the scenario ,
I have a schema with a table in it. I have granted select on that table to a role.
grant select on user1.example_table to example_role;
I then grant that role to a user:
grant example_role to user2;
Then user2 wants to create a view on top of that table:
create or replace view user2.example_view as
select *
from user1.example_table;
That throws an error however:
ORA-01031: insufficient privileges
Why though? If they have select permission via the role, why can they not then create a view on that object?
I found that I had to grant the object directly to the user before it would work.
grant select on user1.example_table to user2;
why this is so,
Thanks,
uday
Edited by: udayjampani on May 16, 2012 4:42 PM