记个MySql的日期函数date_sub(now(), interval 7 day)

1、什么意思

select date_sub(now(), interval 7 day)  from products;
select now()  from products;

2、能做什么？

2.1、做个周统计啥的！

    /**
     * 前台，获取本周热销商品
     * @return
     */
    @MapKey("id")
    List<Map<String, Object>> getWeekHotProduct();

    <!--前台，获取本周热销商品-->
    <select id="getWeekHotProduct" resultType="java.util.Map">
        select products.id as id,products.name as name, products.imgurl as imgurl,SUM(orderitem.buynum) as totalsalnum
                from orderitem,orders,products
                where orderitem.order_id = orders.id
                and products.id = orderitem.product_id
                and orders.paystate=1
                and orders.ordertime > date_sub(now(), interval 7 day )
                group by  products.id,products.name,products.imgurl
                order by totalsalnum desc
                limit 0,2
    </select>

2.2、核心

 and orders.ordertime > date_sub(now(), interval 7 day )