Table design for a matching system

How would I design the tables for a matching system doing something like this:

We have X products which can have Y properties. The number of properties can vary from product to 开发者_C百科product and two products doesn't have to have any similar properties.

My number one goal is to take one product and find the most similar product.

Normally I would do something like this:

create table products
(
   id serial not null primary key,
   name varchar(40)
)

create table properties
(
  id serial not null primary key,
  name varchar(40)
)

create table product_properties
(
  product_id int not null,
  property_id int not null
)

The only way I can think of is to loop through all products, fetch their properties in the loop and compare with the source product. But that doesn't seem very effective.

---

Would something like this be any help?

SELECT *
    FROM products
    WHERE id <> <given product id>
    ORDER BY (SELECT COUNT(*)
                  FROM product_properties
                  WHERE product_properties.product_id = products.id AND
                        product_properties.property_id IN
                                (SELECT property_id
                                     FROM product_property
                                     WHERE product_id = <given product id>))
    LIMIT 1;

This is intended to get the product that has the most properties in common with your original product.