sql server - What's the longest possible worldwide phone number I should consider in SQL varchar(length) for phone

Question

What's the longest possible worldwide phone number I should consider in SQL varchar(length) for phone.

considerations:

• + for country code
• () for area code
• x + 6 numbers for Extension extension (so make it 8 {space})
• spaces between groups (i.e. in American phones +x xxx xxx xxxx = 3 spaces)
• here is where I need your help, I want it to be worldwide

Consider that in my particular case now, I don't need cards etc. number begins with country code and ends with the extension, no Fax/Phone etc. comments, nor calling card stuff needed.

Answer 1

Assuming you don't store things like the '+', '()', '-', spaces and what-have-yous (and why would you, they are presentational concerns which would vary based on local customs and the network distributions anyways), the ITU-T recommendation E.164 for the international telephone network (which most national networks are connected via) specifies that the entire number (including country code, but not including prefixes such as the international calling prefix necessary for dialling out, which varies from country to country, nor including suffixes, such as PBX extension numbers) be at most 15 characters.

Call prefixes depend on the caller, not the callee, and thus shouldn't (in many circumstances) be stored with a phone number. If the database stores data for a personal address book (in which case storing the international call prefix makes sense), the longest international prefixes you'd have to deal with (according to Wikipedia) are currently 5 digits, in Finland.

As for suffixes, some PBXs support up to 11 digit extensions (again, according to Wikipedia). Since PBX extension numbers are part of a different dialing plan (PBXs are separate from phone companies' exchanges), extension numbers need to be distinguishable from phone numbers, either with a separator character or by storing them in a different column.