Phone Number

Worked samples

DuckDB 1.5.5 · finetype 0.6.64

Shape

Length 7 to 30 characters.

Told apart

Background

Origin

The numbering plan behind phone numbers worldwide is ITU-T Recommendation E.164, titled The international public telecommunication numbering plan.^[1] The first issue of E.164 was published in 1988 in Blue Book Fascicle II.2.^[2] E.164 numbers are limited to digits only, with a maximum of fifteen digits.^[2] E.164 divides the digit string into a country code of one to three digits, followed by the subscriber number.^[2]

How a number is written down is a separate ITU-T Recommendation, E.123, titled Notation for national and international telephone numbers, e-mail addresses and web addresses.^[3] The edition of E.123 in force is dated February 2001, and it superseded an edition of November 1988.^[3] E.123 defines the plus sign as the international prefix symbol, written before the country code.^[4] In international notation, E.123 says only spaces should be used to separate groups of digits.^[4] E.123 uses parentheses in national notation to mark digits that are sometimes not dialled, such as an area code.^[4] Parentheses are not allowed in E.123's international notation.^[4]

Use

RFC 3966, which defines the tel URI, allows phone numbers to contain visual separators.^[5] RFC 3966 says visual separators merely aid readability and are not used for URI comparison or placing a call.^[5] In RFC 3966, globally unique numbers are identified by the leading + character.^[5] RFC 3966 identifies phone extensions with an extension parameter.^[5] Strip the separators and keep the digits, the leading plus and any extension apart before comparing or deduplicating numbers. (Meridian's view)

A number without a country code cannot be made international safely unless you know which country the record belongs to, so carry that context alongside the column. (Meridian's view) Google's libphonenumber is a common Java, C++ and JavaScript library for parsing, formatting and validating international phone numbers.^[6] libphonenumber formats the Swiss number 044 668 18 00 as +41 44 668 18 00 in international form and +41446681800 in E.164 form.^[6] libphonenumber's isPossibleNumber check uses only length information, while isValidNumber uses length and prefix information for a region.^[6] A pattern match only shows that a value looks like a phone number; use a library with per-country rules when you need to know whether it could be a real one. (Meridian's view)

In the North American Numbering Plan, only 555-0100 through 555-0199 are now specifically reserved for fictional use.^[7]

Where you'll meet it

OpenStreetMap asks for phone numbers in international (ITU-T E.164) format, written with a plus sign, country code, area code and local number.^[8] OpenStreetMap separates multiple phone numbers in one phone tag with a semicolon.^[8]

Sources

1. [1]E.164 : The international public telecommunication numbering plancatalogue entry
2. [2]E.164secondary source
3. [3]E.123 : Notation for national and international telephone numbers, e-mail addresses and web addressescatalogue entry
4. [4]E.123secondary source
5. [5]RFC 3966: The tel URI for Telephone Numbersstandard
6. [6]google/libphonenumberdocumentation
7. [7]555 (North American Numbering Plan)secondary source
8. [8]Key:phoneorganisation

Detection notes

Use it

Schema

Aliases