-- типы продуктов
create table product_types (
    n number,
    dsc varchar2( 100 )
);

-- продукты
create table products (
    n number,
    up number,  -- ref to product type
    price number,
    n1 number,
    n2 number, 
    ..............
    s1 varchar2(xxx), 
    s2 varchar2(xxx),
    .............
)

-- заявки на покупку
create table requests (
    n number,  -- s/n
    r_products number,  -- ref to products
    status number  -- state of request
)

-- счета
create table invoices (
    up number,  -- ref to requests
    ............
)

-- Для доступа к обуви
create or replace view v$boots 
as select p.n,
          p.n1 as size
     from products p
    where p.up = GC_PRODUCTTYPEBOOT;

-- Для доступа к машинам
create or replace view v$cars 
as select p.n,
          p.s1 as enginesn
     from products p
    where p.up = GC_PRODUCTTYPECAR;