select t1.*,
       coalesce(v_t2.sum_summa_t2, 0 ) as sum_summa_t2,
       coalesce(v_t3.sum_summa_t3, 0 ) as sum_summa_t3,
       coalesce(v_t2.sum_summa_t2, 0 ) + coalesce(v_t3.sum_summa_t3, 0 ) as total_summa_t2_t3
  from t1
  left outer join
       (
          select t1_id,
                 sum(summa) as sum_summa_t2
            from t2
           group by t1_id 
       ) v_t2
    on t1.t1_id = v_t2.t1_id
  left outer join
       (
          select t1_id,
                 sum(summa) as sum_summa_t3
            from t3
           group by t1_id 
       ) v_t3
    on t1.t1_id = v_t3.t1_id