select er.er_oper_code, erc.name, d.name
from er_regist_oper er
join ovst o on o.vn=er.vn
join er_oper_code erc on erc.er_oper_code=er.er_oper_code
join doctor d on d.code=er.doctor
where o.vstdate between "2011-01-01" and "2011-01-31" and er.er_oper_code = "36"