I am not arguing against surrogate keys in general. They are obviously very useful _internally_ to introduce a level of indirection. But if they are used _internally_ then it doesn't really matter if they are UUIDs or sequence numbers or whatever - it is just an implementation detail.
What I claim is that surrogate keys are problematic as _externally visible_ identifiers.
> Okay, then lets do an exercise here. A user gives you a transaction ID, and you have to tell them the date they signed up and the date you first billed them. I think yours is going to be way more complicated.
> Mine is just something like:
> SELECT user_id FROM transactions WHERE transaction_id=X; SELECT transaction_date FROM transactions WHERE user_id=Y ORDER BY transaction_date ASC LIMIT 1; SELECT signup_date FROM users WHERE user_id=Y;
I think you are missing the actual problem I am talking about: where does the user take the transaction ID from? Do you expect the users to remember all transaction IDs your system ever generated for them? How would they know which transaction ID to ask about? Are they expected to keep some metadata that would allow them to identify transaction IDs? But if there is metadata that enables identification of transaction IDs then why not use it instead of transaction ID in the first place?
