统计每日单量MySQL语句，进行XY轴展示

当我们遇到sql查询结果集进行横纵坐标展示时要用到分组函数，例子如下：
– 每日单量
select DATE_FORMAT(createtime,‘%Y-%m-%d’) as days,count() count from ibt_shop_order group by days;
– 每周单量
select DATE_FORMAT(createtime,‘%Y-%u’) as weeks,count() count from ibt_shop_order group by weeks;
– 每月单量
select DATE_FORMAT(createtime,‘%Y-%m’) as months,count(*) count from ibt_shop_order group by months;