Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Products ( product_name VARCHAR, product_id VARCHAR )
TABLE: CREATE TABLE Order_items ( product_id VARCHAR )

### Question ###
Show all product names without an order.

### Accurate SQL ###

SELECT product_name FROM Products EXCEPT SELECT T1.product_name FROM Products AS T1 JOIN Order_items AS T2 ON T1.product_id = T2.product_id