How Can I Extract Digits from Alphanumeric Strings in MySQL?

Extract numbers from alphanumeric strings in MySQL

In database programming, extracting specific data from unstructured or mixed-type strings is a common task. MySQL provides a variety of functions and techniques for this purpose, including the ability to separate numbers from strings.

One way to extract a number from a string is to take advantage of MySQL's cast functionality. By using the CAST() function, you can implicitly convert a string to a numeric type, discarding non-numeric characters. For example, CAST('1234abc' AS UNSIGNED) returns 1234.

Another way is to use a custom function. You can create a reusable solution for extracting numbers by defining a function that iterates over the input string, checks the numeric value of each character, and concatenates the numbers into a new string. Consider the following function:

<code class="language-sql">CREATE FUNCTION `ExtractNumber`(in_string VARCHAR(50)) 
RETURNS INT
NO SQL
BEGIN
    DECLARE ctrNumber VARCHAR(50);
    DECLARE finNumber VARCHAR(50) DEFAULT '';
    DECLARE sChar VARCHAR(1);
    DECLARE inti INTEGER DEFAULT 1;

    IF LENGTH(in_string) > 0 THEN
        WHILE(inti <= LENGTH(in_string)) DO
            SET sChar = SUBSTR(in_string, inti, 1);
            IF sChar BETWEEN '0' AND '9' THEN
                SET finNumber = CONCAT(finNumber, sChar);
            END IF;
            SET inti = inti + 1;
        END WHILE;
        RETURN CAST(finNumber AS UNSIGNED);
    ELSE
        RETURN 0;
    END IF;    
END</code>

After defining a function, you can call it in a query to extract numbers from any string. For example, the following query will return the number 1234:

<code class="language-sql">SELECT ExtractNumber("abc1234def") AS number;</code>

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