SET ROLE Syntax Elements - Teradata Vantage

role_name: Name of the role to set as the current role for a session.; You can use the SET ROLE role_name syntax to enable an externally-assigned role plus any of its nested database roles within a session while disabling all other roles.
EXTERNAL: All external roles mapped to the user are to be made active for the session.; The EXTERNAL keyword is useful only for directory users who are mapped to both a user object and one or more external role objects in the directory, where the system defaults to the privileges for the mapped user.; If the directory user is mapped only to external role objects and not mapped to a database user object, all the external roles are active by default.
NONE: Disables the current role, whether directory- or database-assigned, for a session.
NULL: Null role is to be made current for the session.
ALL: All the roles that have been directly and indirectly granted to a user, whether directory- or database-assigned, become current and active.