drop table x;

create table x
(
  key  int primary key,
  data int
);
insert into x values(1,1);
insert into x values(2,2);
insert into x values(3,3);


create materialized view a
 build immediate
 refresh complete start with sysdate next sysdate + 1/48
 as select key, sum(data)
     from x
     group by key;