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

User · Answer

As for  quot phone numbers quot  you should really consider the difference between a  quot subscriber number quot  and a  quot dialling number quot  and the possible formatting options of them  A subscriber number is generally defined in the national numbering plans  The question itself shows a relation to a national view by mentioning  quot area code quot  which a lot of nations don t have  ITU has assembled an overview of the world s numbering plans publishing recommendation E 164 where the national number was found to have a maximum of 12 digits  With international direct distance calling  DDD  defined by a country code of 1 to 3 digits they added that up to 15 digits     without formatting  The dialling number is a different thing as there are network elements that can interpret exta values in a phone number  You may think of an answering machine and a number code that sets the call diversion parameters  As it may contain another subscriber number it must be obviously longer than its base value  RFC 4715 has set aside 20 bcd-encoded bytes for  quot subaddressing quot   If you turn to the technical limitation then it gets even more as the subscriber number has a technical limit in the 10 bcd-encoded bytes in the 3GPP standards  like GSM  and ISDN standards  like DSS1   They have a seperate TON NPI byte for the prefix  type of number   number plan indicator  which E 164 recommends to be written with a  quot   quot  but many number plans define it with up to 4 numbers to be dialled  So if you want to be future proof  and many software systems run unexpectingly for a few decades  you would need to consider 24 digits for a subscriber number and 64 digits for a dialling number as the limit     without formatting  Adding formatting may add roughly an extra character for every digit  So as a final thought it may not be a good idea to limit the phone number in the database in any way and leave shorter limits to the UX designers

User · Answer

In the GSM specification 3GPP TS 11 11  there are 10 bytes set aside in the MSISDN EF  6F40  for  dialing number    Since this is the GSM representation of a phone number  and it s usage is nibble swapped   and there is always the possibility of parentheses  22 characters of data should be plenty   In my experience  there is only one instance of open close parentheses  that is my reasoning for the above

User · Answer

It s a bit worse  I use a calling card for international calls  so its local number in the US   account   6 digits    pin  4 digits     pause    what you described above   I suspect there might be other cases

User · Answer

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

User · Answer

Well considering there s no overhead difference between a varchar 30  and a varchar 100  if you re only storing 20 characters in each  err on the side of caution and just make it 50

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

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