จริงๆ ก็น่าจะได้นะครับ งั้นลอง
select pt.*,ov.*
from vn_stat ov ,patient pt ,ovst ovst
where ov.vn=ovst.vn and pt.hn=ov.hn and ov.vstdate between "2010-01-01" and "2010-04-30" and ov.hn=pt.hn
and ov.age_y>= 0
and ov.age_y<= 0
and ov.pcode in (
"AA"
,"AB"
,"AC"
,"AD"
,"AE"
,"AF"
,"AG"
,"AH"
,"AI"
,"AJ"
,"AK"
,"AL"
,"UC"
)