select distinct(hn) as hn,icd10 ,vstdate as date from ovstdiag
where vstdate BETWEEN "2012-10-01" AND "2013-03-07" and icd10 like "C%"
union
select distinct(ip.hn) as hn,i.icd10 ,ip.dchdate as date from iptdiag i,ipt ip
where i.an=ip.an and ip.dchdate BETWEEN "2012-10-01" AND "2013-03-07" and i.icd10 like "C%"