select
nullif(B.firstname , A.firstname) as a,
nullif(B.middlename , A.middlename) as b,
nullif(B.lastname , A.lastname) as c,
nullif(B.addr1 , A.addr1) as d,
nullif(B.addr2 , A.addr2) as e,
nullif(B.city , A.city) as f,
nullif(B.state , A.state) as g,
nullif(B.zip , A.zip) as h...