How to Use Regexp in MySQL Replace Commands?

Question

My goal is to replace the links in the database with a catchall link. I generally use the REPLACE command for replacing string in the database, but this time I am having dif

Answer 1

Short answer: you can't with base MySQL.

Long answer: this previous SO question, which mentions that you could do it with a UDF (user-defined function). However, this requires re-building MySQL to include the udf.

Answer 2

REPLACE() does text replacement. There is no regular expression replacement in MySQL.

Answer 3

As others have mentioned already, you can't do this in MySQL. However, this appears to be a one time operation you need to do so I wrote you a quick and dirty little php script to do the job. It assumes your node_revisions table has a primary key column called 'id'. If not, edit appropriately. Also, don't forget to change the database host, username, password and database name at the top of the script to match your configuration.

<?php
$host = '127.0.0.1';
$username = 'root';
$password = 'password';
$database = 'test';

$conn = mysql_connect($host, $username, $password);

if (!$conn) {
    echo "Unable to connect to DB: " . mysql_error();
    exit;
}

if (!mysql_select_db($database)) {
    echo "Unable to select " . $database . ": " . mysql_error();
    exit;
}

$sql = "SELECT * FROM node_revisions";

$result = mysql_query($sql);

if (!$result) {
    echo "Could not successfully run query ($sql) from DB: " . mysql_error();
    exit;
}

if (mysql_num_rows($result) == 0) {
    echo "No rows found, nothing to print so am exiting";
    exit;
}

while ($row = mysql_fetch_assoc($result)) {
    $id = $row['id'];
    $body = $row['body'];
    $teaser = $row['teaser'];
    $body = preg_replace('/http:\/\/.*?\.pdf/', '/migration-update', $body);
    $teaser = preg_replace('/http:\/\/.*?\.pdf/', '/migration-update', $teaser);
    $sql = "UPDATE node_revisions set body='" . mysql_real_escape_string($body) . "', teaser='" . mysql_real_escape_string($teaser) . "' where id=" . $id;
    mysql_query($sql);
}

mysql_free_result($result);
mysql_close($conn);
?>

Note also that I used a non-greedy modifier on the regular expressions so that if you have multiple pdf urls in a body or teaser field, you won't lose everything in between them.