按月分组：select date_format(o.orderdate,'%y%m') weeks,count(*) count from orders o group by weeks;
按周分组： select date_format(o.orderdate,'%y_%u') weeks,count(*) count from orders o group by weeks;
按季度分组：select concat(year(o.orderdate),'_',quarter(o.orderdate)) qu,count(*) count from orders o group by qu;