revoke connect to ttt
grant connect to guest
execute as user = 'ttt'
  select USER_NAME()
revert

execute as user = 'ttt'

execute as login = 'ttt';
use db0
  select USER_NAME();

if exists(select * from sys.objects where object_id = OBJECT_ID('Test'))
  drop table Test
go

create table Test(ID int NOT NULL)
go

insert into Test(ID) values (1)

grant select on Test to guest;

execute as user = 'ttt'
  select * from Test  -- The SELECT permission was denied
revert

execute as user = 'guest'
  select * from Test  -- Возвращена таблица
revert

select *
  from sys.fn_my_permissions(null, 'database')

revoke connect to ttt
grant connect to guest
execute as user = 'ttt'
  select USER_NAME()
revert

revoke connect to ttt
revoke connect to guest
execute as user = 'ttt'
  select USER_NAME()
revert