CREATE TABLE coupons (
    id                serial  not null primary key,
    "name" varchar not null,
    "code" varchar not null,
    "value" int not null default 0
);

create table additional_products (
    id                serial  not null primary key,
    parent_product_id int references products (id) not null,
    free_product_id int references products (id) not null
);

create table addtional_items (
    id                serial  not null primary key,
    parent_product_id int references products (id) not null,
    "name" varchar not null
);