分组统计

1）按天统计：

select DATE_FORMAT(start_time,'%Y%m%d') days,count(product_no) count from test group by days; 

2）按周统计：

select DATE_FORMAT(start_time,'%Y%u') weeks,count(product_no) count from test group by weeks; 

3）按月统计:

select DATE_FORMAT(start_time,'%Y%m') months,count(product_no) count from test group bymonths;