How Can I Efficiently Strip Non-Numeric Characters from Strings for MySQL Comparisons?

Stripping Non-Numeric Characters in MySQL String Comparison

When comparing strings in MySQL, it's often necessary to remove non-numeric characters that could interfere with the match. To perform this operation, we can't rely on PHP functions like preg_replace directly in MySQL queries.

Instead, we can create a custom MySQL function to strip non-digit characters from a given string. Here's an example function:

DROP FUNCTION IF EXISTS STRIP_NON_DIGIT;
DELIMITER $$
CREATE FUNCTION STRIP_NON_DIGIT(input VARCHAR(255))
   RETURNS VARCHAR(255)
BEGIN
   DECLARE output   VARCHAR(255) DEFAULT '';
   DECLARE iterator INT          DEFAULT 1;
   WHILE iterator <p>This function takes a VARCHAR input and iterates through each character, checking if it's a digit. If it is, the character is appended to the output variable.</p><p>With this function in place, we can strip non-numeric characters from a string and use it to compare against numeric values in our MySQL query, as follows:</p><pre class="brush:php;toolbar:false">SELECT * FROM foo WHERE STRIP_NON_DIGIT(bar) = '12345'

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