mySQL Relational Tables Say I have 3 tables Products, Orders and Orders Product

Products Table

ID | StockNum | Description | Price
4  | 452SB    | Black       | 45.65
5  | 752SA    | Green       | 17.12


Orders Table

ID  | OrderNum | Total  |
14  | 12312    | 79.89  | 
15  | 12313    | 45.65  | 


Orders Product Table

ID  | OrderID  | Product  | Qty   | 
45  | 14       | 452SB    | 1     |
46  | 14       | 752SA    | 2     |
47  | 15       | 452SB    | 1     |


If product information changes (Price or Description) this would throw off all previous order information, whats the best solution for this?. Also does it make more sense to be storing the product ID instead of the StockNum? 

** Update **
Does This Make More Sense?  Also everything marked with ID at the end is FK

Products Table

ID | StockNum | ProductDetailsID |
4  | 452SB    | 8                |
5  | 752SA    | 9                |

Products Details Table

ID | Description | Price
8  | Black       | 45.65
9  | Green       | 17.12


Orders Table

ID  | OrderNum | Total  |
14  | 12312    | 79.89  | 
15  | 12313    | 45.65  | 


Orders Product Table

ID  | OrderID  | Product  | Qty   | ProductDetailsID |  
45  | 14       | 452SB    | 1     | 8                |
46  | 14       | 752SA    | 2     | 9                |
47  | 15       | 452SB    | 1     | 8                |
You can add the fields Price and Description to the Orders Product table and copy the values when you create the row. This allows you to read the values as they were by the time of the order execution

Orders Product Table

ID  | OrderID  | Product  | Qty   | Description | Price
45  | 14       | 452SB    | 1     | Black       | 45.65
46  | 14       | 752SA    | 2     | Green       | 17.12
47  | 15       | 452SB    | 1     | Black       | 45.65


And yes, using Keys is always preferable 

UPDATE

About foreign keys. Display them like this

Products Table

ID | StockNum | ProductDetailsID |
4  | 452SB    | 8                |
5  | 752SA    | 9                |

Products Details Table

ProductDetailsID | Description | Price
8                | Black       | 45.65
9                | Green       | 17.12