is based on system-wide policies that cannot be changed by individual users. In this approach each database object is assigned a security class and each user is assigned a clearance for a security class, and rules are imposed on reading and writing of database objects by users. The DBMS determines whether a given user can read or write a given object based on certain rules that involve the security level of the object and the clearance of the user. These rules seek to ensure that sensitive data can never be passed on to another user without the necessary clearance. The SQL standard does not include support for MAC