Postal addresses seem to be easy:
– Name and/or Company
– Street and/or PostBox
– ZIP Code
This is true in Germany or Switzerland and a few other countries. I would like to add, that in some large buildings it can be a good idea to add the apartment number, but these buildings are rare in these two countries and the name is really almost always sufficient.
For relational databases please keep in mind, that these fields may get just a bit or even a lot longer than we anticipated. US-ZIP-Codes are now something like NY-11713-5532. And others may be longer. How long are names, street names and names of villages and towns? Even the country part, which seems to be relatively easy, brings some challenges. Countries like Switzerland and Germany and Canada are no problem. But what about semi-independent countries like Guernsey, Jersey, …? And what about areas, that are de-jure part of another country, but de-facto an independent country? Or an independent country that is not accepted by each country? There are lists of countries that we can find and usually they include also the „semi-independent“ and „semi-accepted“ countries. But it is a good idea to check if the list is complete enough for our purpose. I would not recommend to define it yourself.
But now the other parts of the address: If we want to describe the location where a person lives, and this person does not live in a housing area, but for example in a nomadic life style, it becomes a bit harder. Or we might observe a different number of lines for the address. Or even that streets are not named consistently and the only relyable address is a postbox. Many countries do not write the names on the door and on the letterbox, but just an apartment number. So this number with some word for „apartment“ that is understood by the local post officer with possibly limited language skills is needed. Also in some countries there are a lot of buildings for „streetname 3053A“, so we need to add the building number also.
My point is, that postal addresses are not as easy as it might seem. So I recommend to do some research in the internet to find a library or a documentation that handles this or can be used as a basis instead of trying to invent a new wheel that will probably be incomplete and suffer from its insufficiencies at some point. It is sometimes more important to recognize which seemingly trivial problems are actually harder than being able to invent solutions for such problems. We should invest our energy on solving problems that have not been solved with publicly available documentations or even libraries and that make up our business. In this case the actual implementation is rather trivial, but the specification of the requirements is the hard part, so it is enough to find some useful documentation for this. It might of course be sufficient to handle only for example French addresses, if the system will never be dealing with foreign addresses, but the experience shows that at least some thinking about what it means to extend the system later are a good idea.
And please, handle too long entries properly instead of displaying a stack trace on the end users screen or even providing a spot to attack the server.