mysql order by

order by
排序：在结果集出来之后才有意义 必须在where ,group by ，having 之后
desc（降序）/asc(升序)

用字段排序 

用shop_price 降序排列

select goods_name,cat_id,shop_price from goods where cat_id=4 order by shop_price desc;

多个排序选择，先根据cat_id,然后shop_price

select cat_id,shop_price,goods_name from goods order by cat_id ,shop_price;

limit限制 limit [pos, 可选偏移量] 数量 

升序排列 取出前十名

select goods_id,goods_name from goods where cat_id=3 order by shop_price asc limit 10;

价格最高的前五名

mysql> select goods_name ,shop_price from goods order by shop_price desc limit 0,5;

mysql> select goods_name ,shop_price from goods order by shop_price desc limit 5;
+----------------+------------+
| goods_name | shop_price |
+----------------+------------+
| 多普达Touch HD | 5999.00 | 
| 诺基亚N96 | 3700.00 | 
| 诺基亚N85 | 3010.00 | 
| testPhone | 3000.00 | 
| 夏新T5 | 2878.00 | 
+----------------+------------+

价格最高的 从第三名开始的三名（或者说是第三名到第五名）

mysql> select goods_name ,shop_price from goods order by shop_price desc limit 2,3;
+------------+------------+
| goods_name | shop_price |
+------------+------------+
| 诺基亚N85 | 3010.00 | 
| testPhone | 3000.00 | 
| 夏新T5 | 2878.00 | 
+------------+------------+

取出价格最高的商品

mysql> select goods_name ,shop_price from goods order by shop_price desc limit 1;
+----------------+------------+
| goods_name | shop_price |
+----------------+------------+
| 多普达Touch HD | 5999.00 | 
+----------------+------------+

技巧 ：[判断where] [分组group_by] [过滤having] [排序order by] [筛选limit]

取出每个类型中 最新的产品

select cat_id, goods_id ,goods_name from(
(select cat_id,goods_id ,goods_name from goods order by cat_id desc,goods_id desc ) as tmp
)group by cat_id order by cat_id desc;

select cat_id,goods_id ,goods_name from goods where goods_id in (
select max(goods_id) from goods group by cat_id 
) order by cat_id desc;

查询出来的结果可以是
单列单行 可以用= 再次过滤
单列多行 可以用in 再次过滤
多列多行 可以用from 再次过滤

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