Phone Number Columns in a Database

Question

In the last 3 companies I\'ve worked at, the phone number columns are of type varchar(n). The reason being that they might want to store extensions (ext. 333). But in every

Answer 1

Quick test: are you going to add/subtract/multiply/divide Phone Numbers? Nope. Similarly to SSNs, Phone Numbers are discrete pieces of data that can contain actual numbers, so a string type is probably most appropriate.

Answer 2

Stripping some characters and allowing others may have an impact if the database table is going to drive another system, e.g. IP Telephony of some sort. Depending on the systems involved, it may be legitimate to have etc.333 as a suffix, whereas the developers may not have accounted for "-" in the string (and yes, I am guessing here...)

As for storing as a varchar rather than an int, this is just plain-ole common sense to me. As mentioned before, leading zeros may be stripped in an int field, the query on an int field may perform implicit math functions (which could also explain stripping "-" from the text, you don't want to enter 555-1234 and have it stored as -679 do you?)

In short, I don't know the exact reasoning, but can deduce some possibilities.

Answer 3

one point with storing phone numbers is a leading 0.

eg: 01202 8765432

in an int column, the 0 will be stripped of, which makes the phone number invalid.

I would hazard a guess at the - being swapped for spaces is because they dont actually mean anything

eg: 123-456-789 = 123 456 789 = 123456789

Answer 4

What I like to do if I know the phone numbers are only going to be within a specific region, such as North America, is to change the entry into 4 fields. 3 for area code, 3 for prefix, 3 for line, and maybe 5 for extension. I then insert these as 1 field with '-' and maybe an 'e' to designate extension. Any searching of course also needs to follow the same process. This ensures I get more regular data and even allows for the number to be used for actually making a phone call, once the - and the extension are removed. I can also get back to original 4 fields easily.