7_查询之where

查询

条件判断

select 5种子句：

where 条件查询

group by 分组

having 筛选

order by 排序

limit 限制结果条数

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where

1.运算符:

<

<=

=

!=  <>不等于有两种表示

>=

>

inin (4,5)

betweenbetween 2000 and 3000

取出goods_id是4和5的商品：

select goods_id,goods_name from goods where goods_id in (4,5);

取出goods_price是2000到3000之间的商品：

select goods_price,goods_name from goods where goods_price between 2000 and 3000;

2.逻辑运算符

not 或 ！

or  或 ||

and 或 &&

取出goods_price是2000到3000之间的商品，和goods_price是500-1000之间的商品：

select goods_name,goods_price from goods

where goods_price >=2000 and goods_price<=3000 or goods_price >=500 and goods_price <=1000;

3.模糊查询

like "诺基亚%"%是通配任意字符

like "诺基亚N__"_是单个字符

取出所有"诺基亚"开头的商品：

select goods_id,goods_name from goods where goods_name like "诺基亚%";

取出所有"诺基亚NXX"开头的，N后面有两个字符的商品：

select goods_id,goods_name from goods where goods_name like "诺基亚N__";