Rename column in VIEW

Question

When creating views, we can change the column names of tables, which is based view. I would like to know, how it has a purpose of the SECURITY. I need yours opinion or example on this question. Thanks.

Answer 1

Hi,
Views can enforce security when users have privileges on a view, but do not have privileges on the base table(s) (that is, the table(s) referenced in the CREATE VIEW statement.
For example, say only a few users (in a role called sepcial_users) are allowed to see the sal column of the scott.emp table. All users should be allowed to see the other columns of scott.emp.
In that case, you might create a view like this:
CREATE OR REPLACE VIEW  emp_public
AS
SELECT  empno, ename, job, mgr, hiredate, comm, deptno   -- All columns EXCEPT sal
FROM    scott.emp;
GRANT  SELECT  ON  emp_public  TO PUBLIC;
GRANT  SELECT  ON  scott.emp  TO special_users;Now, everybody on the system can query the view emp_public, which is just like scott.emp except that emp_public does not have a sal column.
Here's another example. Say each Oracle user who is in the scottt.emp table (that is, whose user name is the same as emp.ename) should be allowed to see sals in his own department. Anyone, including users who are not in the emp table, is allowed to see all the other columns. Here's one way to do that with a view:
CREATE OR REPLACE VIEW  emp_public
AS
SELECT  empno, ename, job, mgr, hiredate
,      CASE
         WHEN  deptno IN ( SELECT  deptno
                           FROM    scott.emp
                     WHERE   ename     = USER
         THEN  sal
         ELSE  NULL     -- Default, but it doesn't hurt to say it
     END     AS sal
,     comm, deptno
FROM    scott.emp;This is kind of like how the data dictionary views work.
Views that start with DBA_ have no security built into them. For example, DBA_TABLES has information about all tables in the database. Security has to be handled by grants, which is why (usually) only a view people are allowed to use it.
Views that start with ALL_ have some security built into them. Everyone is allowed to use ALL_TABLES, but the built-in security makes the view only include a fraction of the rows that are in DBA_TABLES.
Views that start with USER_ have even tighter security built into them. Everyone is allowed to use USER_TABLES, but everyone sees something different (that is, only their own tables) when they use it.