msql 统计函数 and 分组统计

平均数

select  avg(shop_price) from goods;

求最大最小

select min(shop_price) from goods;

select max(shop_price) from goods;

求行数

select count(*) from goods;

分组统计

group 是需要耗费资源的  会有排序

slect cat_id,avg(shop_price) from goods group by cat_id;

select cat_id,count(*) from goods group by cat_id;

select cat_id,max(good_price)) from goods group by cat_id;