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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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