How do you reference capture groups in MySQL regex?

Capturing Groups in MySQL Regex

When using regular expressions (regex) in MySQL, it's often necessary to extract specific portions of the matched text into capture groups. However, unlike other languages, MySQL does not provide a direct syntax for referencing these groups in subsequent regex operations.

Question:

How can capture groups be referred to in a MySQL regex?

Answer:

In MySQL, capture groups are referenced using a special notation. For versions MySQL 8 and higher:

• The $n syntax is used, where n is the number of the capture group (e.g., $1 for the first group).

Example:

SELECT REGEXP_REPLACE('stackoverflow','(.{5})(.*)','');
-- Returns "overflowstack"

This regex captures two groups:

1. The first five characters using the capture group (.{5})
2. The remaining characters using the capture group (.*)

The REGEXP_REPLACE() function then replaces the original string with the second group followed by the first group, effectively reversing the order of the first five characters.

Note: For MariaDB, the notation for referencing captures is slightly different, using 1, 2, etc. instead of $1, $2.

The above is the detailed content of How do you reference capture groups in MySQL regex?. For more information, please follow other related articles on the PHP Chinese website!