分別把 計算各自的 
1、點擊量/點擊量均值  
2、銷售量/銷售量均值

兩者相加，可以得到一個簡單評分

又有問題了，豬肉的評分不應該比五花肉多。

因此我們要加入簡單的權重，譬如點擊量評分占30%。銷售量評分占70%

select p_type,p_name, (p_view/view_avg)*0.3+(sales/sales_avg)*0.7 from (
select a.*,b.sales_avg,c. view_avg  from (select   p_type,a.p_name,a.p_view, IFNULL(b.p_sales,0) as sales from products a  
   LEFT JOIN products_sales b
on a.p_id=b.p_id
GROUP BY  a.p_type,a.p_name order by a.p_type desc, a.p_view desc 
) a ,
( select p_type,round(sum(sales)/count(*),0) as sales_avg from ( select  p_type, a.p_name,a.p_view, IFNULL(b.p_sales,0) as sales from products a  
   LEFT JOIN products_sales b
on a.p_id=b.p_id
GROUP BY  a.p_type,a.p_name order by a.p_type desc, a.p_view desc ) c
where c.sales>0
GROUP BY p_type
)
b,
(select p_type,round(sum(p_view)/count(*),0) as view_avg from products GROUP BY p_type )
c
where a.p_type=b.p_type  and a.p_type=c.p_type ) aa

純SQL實現小算法（輔助決策）_ 計算商品評分、及時補貨