Oracle SQL: UPDATE stement with a FROM clause

drop table if exists tq84_B;
drop table if exists tq84_A;

create table tq84_A (
   id           integer primary key,
   total_val    number(6,2),
   last_updated date
);

create table tq84_B (
    id_A     integer references tq84_A not null,
    val      number(5,2)       not null
);

insert into tq84_A (id) values (1),(2),(3),(4),(5);

insert into tq84_B values
  (1, 189.57),
  (1, 134.12),
  (2,  56.89),
  (2,  78.43),
  (2, 167.26),
  (2,  22.99),
  (3, 115.71),
  (5,  42.15),
  (5, 153.88),
  (5,  96.03);

update
   tq84_A a                 
set
   total_val    = b.sum_val,
   last_updated = sysdate
from (
   select
      id_a,
      sum(val) sum_val
   from
      tq84_B b
    group by
      id_a
) b
where
   a.id = b.id_A
;
  
select * from tq84_A;