你数据库的日期格式是什么样子的?
写2个条件
where 1=1
${if(年="","","and year = '"+年+"'")}
${if(月="","","and month= '"+月+"'")}
或者。
where 1=1
${if(年="","","and left (year,4) in('"+replace(年,",","','")+"')")}
${if(月="","","and rigth(month,2) in('"+replace(月,",","','")+"')")}