MySQL Cookbook, 2nd Edition

Using Patterns to Match Email Addresses or URLs

Problem

You want to determine whether a value looks like an email address or a URL.

Solution

Use a pattern, tuned to the level of strictness you want to enforce.

Discussion

The immediately preceding sections use patterns to identify classes of values such as numbers and dates, which are fairly typical applications for regular expressions. But pattern matching has such widespread applicability that it’s impossible to list all the ways you can use it for data validation. To give some idea of a few other types of values that pattern matching can be used for, this section shows a few tests for email addresses and URLs.

To check values that are expected to be email addresses, the pattern should require at least an @ character with nonempty strings on either side:

/.@./

That’s a pretty minimal test. It’s difficult to come up with a fully general pattern that covers all the legal values and rejects all the illegal ones,^[13] but it’s easy to write a pattern that’s at least a little more restrictive. For example, in addition to being nonempty, the username and the domain name should consist entirely of characters other than @ characters or spaces:

/^[^@ ]+@[^@ ]+$/

You may also want to require that the domain name part contain at least two parts separated by a dot:

/^[^@ ]+@[^@ .]+\.[^@ .]+/

To look for URL values that begin with a protocol specifier of http://, ftp://, or mailto:, use an alternation that matches any of them at the beginning of the string. ...