anchor.diff:      }),
       lists:map(fun map_user/1, cqerl:all_rows(Result));
   
  +%% ------------------------------------------------------------------
  +%% @doc Select several users.
  +%% @end
  +%% ------------------------------------------------------------------
   select_user(List) ->
       {ok, Client} = get_cqerl_client(),
       {ok, Result} = cqerl:run_query(Client, #cql_query{
  
positive.code:         ]
      }).
  
  select_session(#t_session{} = Session) ->
      {ok, Client} = get_cqerl_client(),
      {ok, Result} = cqerl:run_query(Client, #cql_query{
  
negative.code:         )
      ", [?KEYSPACE, ?TABLE_ROOM]));
  
  %% ------------------------------------------------------------------
  %% @doc Create the `message` table.
  %% @end
  %% ------------------------------------------------------------------
  create_table(message) ->
      {ok, Client} = get_cqerl_client(),
      {ok, _} = cqerl:run_query(Client, io_lib:format("
  