Do Addresses Have a Unique Identifier?
The "Fast Lane" Answer
There is no truly unique identifier (yet) for a given address. The Delivery Point Barcode (DPBC), while unique for most addresses is problematic because it is unstable. ZIP Codes are subject to change whenever needed by the US Postal Service, which would alter the DPBC. Your best bet for a unique identifier for any given address might be to take the standardized version of the address (minus the ZIP Code) and present it as a string. For example,
The "Scenic Route" Answer
Many people need to identify address duplicates in their databases. This can be difficult since you may have the same address formatted differently. For example:
(a) 360 N Bedford Suite 204 Beverly Hills CA 90210-5124 (b) 360 North Bedford Dr # 204 Beverly Hills CA 90210-5124
Because of the different formatting, they're hard to catch as duplicates. However, you'll notice that the Delivery Point Barcode (DPBC) is the same for both. This is because they are actually the same address.
Note: There is no truly unique identifier (yet) for a given address. 4% of ZIP Codes change each month. Boundaries are realigned as delivery routes change. Remember, the USPS owns the ZIP Codes and they change them anytime it is convenient for them. Since the DPBC is based on the ZIP Code, if that changes, the DPBC would change. Thus, today 902105124547 could represent one specific address but tomorrow it could be represented by a different DPBC due to a ZIP Code change.
What doesn't change, usually, is the address of the house. The standardized version of the address, 360 N Bedford Dr Ste 204 Beverly Hills CA, is probably going to be the address for the building and apartment for a long time to come. That's much more stable than including the ZIP Code, which can change without notice. Cities, on the other hand, rarely change their name. States very rarely change their name, and the state abbreviation can't get any smaller than two characters. In order to change the primary number from 360 to 380, the building would need to move. So a better unique identifier might be the standardized address, minus the ZIP Code, as a string: