> What is a “phone number space”? Do you need to call the phone number? Then you probably need to type it. If two phone numbers when typed result in the same n

> What is a “phone number space”? Do you need to call the phone number? Then you probably need to type it. If two phone numbers when typed result in the same number, they are the same. So you probably want to normalize your numbers: remove ( or - or spaces or anything that isn't actually meant to be typed, then you can compare two phone numbers. Of course it doesn't end there. There's another, looser equivalence between phone numbers that are much more useful: if we call both numbers, will they call the same phone? Things like presence vs absence of country codes, area codes and other things could be part of your normalization. But then, you would need to keep the context in which each phone number was collected. For example, if someone in a given city tells they have a phone number, and someone else in another far away city informs the same phone number, they probably refer to different phones (because the area code is likely different) What's better, of course, is to ask for country code and area code in the same form. If all your phone numbers are "fully qualified", then you can just compare them for equality. But this is not always possible So this kind of thing is fuzzy and has edge cases, but getting it right is essential if you want to search for two people with the same phone number (for example). Since there are edge cases, it's important that phone numbers are stored exactly as they were input, and then normalize as a separate column or something.