-- Database schema
| Addresses : address_id [ INT ] primary_key , line_1_number_building [ TEXT ] , city [ TEXT ] , zip_postcode [ TEXT ] , state_province_county [ TEXT ] , country [ TEXT ] | Products : product_id [ INT ] primary_key , product_type_code [ TEXT ] , product_name [ TEXT ] , product_price [ INT ] | Customers : customer_id [ INT ] primary_key , payment_method_code [ TEXT ] , customer_number [ TEXT ] , customer_name [ TEXT ] , customer_address [ TEXT ] , customer_phone [ TEXT ] , customer_email [ TEXT ] | Contacts : contact_id [ INT ] primary_key , customer_id [ INT ] , gender [ TEXT ] , first_name [ TEXT ] , last_name [ TEXT ] , contact_phone [ TEXT ] | Customer_Address_History : customer_id [ INT ] Customer_Address_History.customer_id = Customers.customer_id , address_id [ INT ] Customer_Address_History.address_id = Addresses.address_id , date_from [ TEXT ] , date_to [ TEXT ] | Customer_Orders : order_id [ INT ] primary_key , customer_id [ INT ] Customer_Orders.customer_id = Customers.customer_id , order_date [ TEXT ] , order_status_code [ TEXT ] | Order_Items : order_item_id [ INT ] , order_id [ INT ] Order_Items.order_id = Customer_Orders.order_id , product_id [ INT ] Order_Items.product_id = Products.product_id , order_quantity [ TEXT ] |
-- -- Show the product type codes which have at least two products.

SELECT product_type_code FROM products GROUP BY product_type_code HAVING count(*)  >=  2;