create table booktype
(
   btid   int(5) unsigned zerofill auto_increment not null primary key,
   btname varchar(100) not null unique,
   btnote text
);

create table books
(
   bid int(5) unsigned zerofill auto_increment not null primary key,
   bname char(30) not null,
   isbn char(50) not null,
   author char(30) not null,
   press   text,
   summary text,
   bcount int not null default 0,
   btid   int,
   foreign key(btid) references booktype(btid)
);

（以下红色部分为已经修改）

drop table if exists products;
create table products(
 id  int  not null auto_increment,
 title  varchar(100) not null,
 description text  not null,
 image_url varchar(200) not null,
 price  decimal(10,2) not null,
 date_available  datetime not null,
 primary key(id)
)type=innodb;

drop table if exists line_items;

create table line_items(
 id  int  not null auto_increment,
 product_id int  not null,
 quantity int  not null default 0,
 unit_price decimal(10,2) not null,

 constraint fk_items_product foreign key (product_id) references producets(id),

index(product_id)
 primary key(id)
)type=innodb;