XML XQuery Regex

• XQuery Regex is a pattern matching language used to search for and manipulate text data using regular expressions.
• With XQuery's support for regular expressions, developers can easily parse, search, and manipulate data that matches the given pattern.

Syntax

The basic syntax for XQuery Regex is as follows:

fn:matches($input, $pattern, $flags)

• fn:matches: A built-in function in XQuery that returns true if the given input matches the pattern.
• $input: The input string that needs to be matched using the regex pattern.
• $pattern: The regex pattern to be matched with the input string.
• $flags: Optional parameters used to modify the regex search.

Example

Consider the following XQuery example that matches all the email addresses that end with ".com":

let $emails := ('support@domain.com', 'test@domain.org', 'help@domain.net')
for $email in $emails
where fn:matches($email, '.*\.com$')
return $email

Output

The output of the above example is:

support@domain.com

Explanation

The example above demonstrates the use of XQuery's fn:matches function to search for all email addresses that end with ".com". The regex pattern used in the example is .*\.com$. Here, .* matches any string followed by .com, and $ denotes the end of the string.

The where clause filters the search and only returns the email addresses that match the given pattern. In this case, only the email address support@domain.com matches the pattern.

Use

Some common use cases for XQuery Regex include:

• Parsing and extracting data from unstructured text files.
• Validating user input and enforcing format restrictions.
• Searching for data that matches a particular pattern or criteria.

Important Points

• XQuery supports regular expressions using the fn:matches function.
• The regex pattern can include special characters, such as metacharacters, that have special meanings in XQuery.
• XQuery supports several flags that can be used to modify the search, such as case-insensitive matching and global matching.
• XQuery supports other regex-related functions such as fn:replace and fn:tokenize.

Summary

In summary, XQuery Regex is a powerful tool that enables developers to search, extract, and manipulate text data using regular expressions. Understanding the basic syntax and functionality of fn:matches is essential for using regex in XQuery, and it can be a useful tool for parsing and analyzing unstructured data.