Better way to write this query

I have two tables. Both tables have upc and item.

I want to find if for a given upc there is more than one item in either or
both tables. So if one table has a upc with two items or both tables have
the same upc but different item then I want to return a count > 1.

I believe this query would work.

with t1 as (
select 1 as c1, 2 as c2
from sysibm.sysdummy1 a
union all
select 1 as c1, 2 as c2
from sysibm.sysdummy1 b),

t2 as (
select c1,c2
from t1
group by c1,c2)

select count(*) from t2;

Is there a better/easier way to write this query?

Thanks,

Rob