When designing a database schema you often have to make decisions on a fields length. Rather then just guess at a number, use the maximum possible value that could conceivably be used for the field. Below is a chart of common database fields such as email address, city, zip code and country name and the maximum possible length value that can be used.
|Field Name||Character Length||Example|
|email address||254||see RFC5321|
|city||189||Longest City Name is Bangkok in Thai: Krung Thep Mahanakhon Amon Rattanakosin Mahinthara Ayuthaya Mahadilok Phop Noppharat Ratchathani Burirom Udomratchaniwet Mahasathan Amon Piman Awatan Sathit Sakkathattiya Witsanukam Prasit|
|zip code||18||Country with the longest zip code format is Chile with NNNNNNN, NNN-NNNN|
|country||90||Longest country name is Libya’s Arabic name prior to 2013: al-Jam-h-riyyah al-‘Arabiyyah al-L?biyyah ash-Sha‘biyyah al-Ishtir-kiyyah al-‘U-má|