[大数据]MYSQL 寒假自学 2022 六（二）

select的使用

select * from product where pname = '海尔洗衣机';

select * from product where price = 800;
select * from product where price != 800;
select * from product where price <> 800;
select * from product where not (price = 800);


select * from product where price >=60;
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;

-- 查询价格是200或800的所有商品
select * from product where price in(200,800);
select * from product where price = 200 or price = 800;
select * from product where price = 200 || price = 800;

-- 查询含有‘裤’字的所有商品
select * from product where pname like '%裤%';

-- 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'蔻'的商品
select * from product where pname like '_蔻%';
--  _下划线匹配单个字符
-- 查询category_id为null的商品
select * from product where category_id is null;

select * from product where category_id is not null;

select least(10,5,20);
select least(10,5,20) as small_number;

select greatest(10,20,30);
select greatest(10,null,30);

注意，求最大最小值时，如果里面有一个null，结果直接为null，不会进行比较。

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