select * from a
where 1=1
${if(len(year)>0 && len(month)>0,"and year='"+year+"' and month='"+month+"'",if(len(year)>0 && len(month)=0,"and year='"+year+"' ",""))}
有数据汇总的加上 group by
select * from a
where 1=1
${if(len(year)>0 && len(month)>0,"and year='"+year+"' and month='"+month+"' group by year,month",if(len(year)>0 && len(month)=0,"and year='"+year+"' group by month",""))}