order by
order by对最终的结果集进行排序，放在语句where/group by/having后面
1、使用商品价格对搜索结果进行降序排列desc（升序排列asc ）
mysql> select goods_id,goods_name,shop_price from goods where cat_id=4 order by shop_price desc;
2、先按照栏目排序再按照商品价格排序
mysql> select goods_id,goods_name,shop_price from goods where cat_id=4 order by cat_id asc,shop_price desc;
limit
限制显示的条目limit [n],m
n：（可选）偏移量，跳过几行
m：取出条目
1、取出前10行和3到5行
mysql> select goods_id,goods_name,shop_price from goods where cat_id=4 order by shop_price desc limit 10;
mysql> select goods_id,goods_name,shop_price from goods where cat_id=4 order by shop_price desc limit 2,3;
2、取出每个栏目价格最高的
需要使用子查询
mysql> select cat_id,shop_price from (select cat_id,goods_name,shop_price foods order by cat_id,shop_price desc) as tmp group by cat_id;
来源：https://blog.csdn.net/Sudley/article/details/98884296