【笔记】9. 基本查询DQL-分组和分页查询

-- 分组查询
select category_id, count(pid) as num_product, avg(price) as avg_price from product group by category_id having avg_price > 50 order by num_product desc;

-- 分页查询
-- 1. 显示前五条
select * from product limit 5;
-- 2. 从第四条开始显示五条
select * from product limit 3, 5;

-- 从一张表中插入另外一张表的数据
create table mydb1.product2(
	pid int primary key auto_increment,
	pname varchar(20) not null , -- 商品名字
  price double,  -- 商品价格
  category_id varchar(20) -- 商品所属分类
);
insert into product2 values(null,'三菱洗衣机',7000,'c001');
insert into product(pname,price,category_id) select pname,price,category_id from product2