Mysql Datatype for US Zip (Postal Codes)

Question

I am writing a web application, that is US specific, so the format that other countries use for postal codes are not important. I have a list of us zip codes that i am trying to load into a database table that includes the

• 5 digit us zip code
• latitude
• longitude
• usps classification code
• state code
• city

the zip code is the primary key as it is what i will be querying against. i started using a medium int 5 but that truncates the zip codes that have leading zeros.

i considered using a char5 but am concerned about the performance hit of indexing against a char variable.

so my question is what is the best mysql datatype to store zip codes as?

Note: i have seen it in several other questions related to zip codes. I am only interested in US 5 digit zip codes. So there is no need to take other countries postal code formats into consideration.

Answer 1

char(5) is the correct way to go. String indexing is quite fast, particularly when it is such a small data set.

You are correct in that you should never use an integer for a zip code, since it isn't truly numeric data.

Edit to add: Check out this for good reasons why you don't use numbers for non-numerically important data: http://stackoverflow.com/questions/893454/is-it-a-good-idea-to-use-an-integer-column-for-storing-us-zip-codes-in-a-database

Answer 2

go with your medium INT(5) ZEROFILL, it should add the leading zeros for you. No need to impact the index and performance on a formatting issue.

Answer 3

If he makes it Char(6), then he can handle Canadian postal codes as well.

When you consider that there is a maximum of 100,000 5-digit Zip Code and how little space it would take up even if you made the entire table memory-resident, there's no reason not to.