MySQL-运算符
1、算数运算符
类别：+、-、*、/、%
-- 将每件商品价格+10
select pname,price+10 as new_price from product;
-- 将所有商品价格上调10%
select pname,price*1.1 as new_price from product;
2、比较运算符和逻辑运算符
等号
select * from product where pname='海尔洗衣机';
-- 查询价格为800的商品
select * from product where price=800;
不等于
-- 查询价格不是800的商品
select * from product where price!=800;
select * from product where price<>800;
select * from product where not (price=800);
>=、<=、>、<
-- 查询商品大于60的商品信息
select * from product where price>60;
-- 查询商品价格再200到1000的商品
select * from product where price between 200 and 1000;
select * from product where price>=200 and price<=1000;
select * from product where price>=200 && price<=1000;
或
-- 查询商品价格800或200的商品
select * from product where price in(800,200);
select * from product where price=800 or price=200;
模糊匹配like
-- 模糊匹配查询
-- 查询所有包含"裤"字的所有商品
select * from product where pname like '%裤%'; -- %可以匹配多个字符
-- 查询以"海"字开头的所有商品
select * from product where pname like '海%';
-- 查询第二个字为"寇"的商品
select * from product where pname like '_蔻%'; -- 下划线匹配一个字符
查询null和不是null
-- 查询category_id为null的商品
select * from product where category_id is null;
-- 查询category_id不为null的商品
select * from product where category_id is not null;
