The DROP ROLE statement allows you to drop an SQL role.
Only the database owner can drop a role.
For more information on roles, see "Using SQL roles" in the Derby Developer's Guide.
DROP ROLE roleName
Dropping a role has the effect of removing the role from the database dictionary. This means that no session user can henceforth set that role (see SET ROLE statement), and any existing sessions that have that role as the current role (see CURRENT_ROLE function) will now have a NULL CURRENT_ROLE. Dropping a role also has the effect of revoking that role from any user and role it has been granted to. See REVOKE statement for information on how revoking a role may impact any dependent objects.
DROP ROLE reader;