Why use autonumber as a primary key

[Accrj19]

Could someone help me understand why using an autonumber field as a primary key is a good idea?

If you use an autonumber as the PK, won't that allow the possibility of duplicate data being entered into the database? For example, if I have an Orders table, an order could be entered twice and each of these records in the Orders table would have a different autonumber but it would be the same order.

I hope this makes sense. Thanks.

[Rabbit]

Both natural keys and surrogate keys have advantages and disadvantages. It is up to you to decide on a case by case basis which one outweighs the other.

You can refer to this page on wikipedia for more information. https://en.wikipedia.org/wiki/Surrogate_key.

Usually, the advantages of a surrogate key outweigh the advantages of a natural key. Specifically regarding your situation, that is one of the disadvantages of using a surrogate key over the natural key (which I assume is some sort of order number that you calculate). That particular weakness can be removed by placing a unique index on the natural key. Just because you're using a surrogate key doesn't mean that you have no way of ensuring uniqueness on your natural key.

If your order number is never going to change, then that could make it a strong candidate to be the primary key.