declare 
  -- Local variables here
  random_num number;
begin
  -- Test statements here
  for rec in (select id,A,B from test)
  loop
        select trunc(dbms_random.value(1,10))
        into random_num
        from dual;
        
        if random_num <= rec.A
           then 
               update test t set t.B = 1 where t.id = rec.id; 
        end if;
  
  end loop;
  
end;