select ((select count(uni) from send where uni is not null)
       + (select count(mob) from send where mob is not null)
       + (select count(tel) from send where tel is not null)) as total
from dual

------解决方案--------------------
create table a (
  aa number(10),
  bb number(10),
  cc number(10)
)

insert into a values(1,1,0);
insert into a values(1,0,1);
insert into a values(1,0,0);

select sum(aa)+sum(bb)+sum(cc) from a;