Integer vs String in database

Question

When defining datatypes in a database, I have always had a problem with choosing whether to use integers or strings to store certain \'numerical\' data.

Say I am bui

Answer 1

Well as far as postcodes go, this is a typical UK postcode:

EC2R 6PK

In university my databases lecturer told me something that has stuck with me and still holds 15+ years later:

If you perform arithmetic on it, store it as a number. Otherwise it's a string.

Frankly I don't think you can go wrong with that advice.

Obviously you don't perform arithmetic on postcodes, therefore they're strings.