MySQL: Get formatted ISO date from string with european date (can be easily extended to other formats)

getSqlDate.sql

/**
 * This script has been tested in MySQL 5.1.37.
 * It might work with other SQL-DBMS as well.
 */
DROP FUNCTION IF EXISTS getSqlDate;
DELIMITER //

CREATE FUNCTION getSqlDate(str VARCHAR(10))
RETURNS VARCHAR(10) DETERMINISTIC
CASE
    WHEN (str REGEXP '^[0-3][0-9]\.[01][0-9]\.[0-9]{4}$') THEN
        /* European: 01.06.2011 */
        RETURN STR_TO_DATE(str, GET_FORMAT(DATE, 'EUR'));
    WHEN (str REGEXP '^[0-9]{4}-[01][0-9]-[0-3][0-9]$') THEN
        /* ISO 8601: 2011-06-01 */
        RETURN str;
    ELSE
        RETURN 'ERR';
END CASE;
//

DELIMITER ;

SELECT 
    @eur := '01.01.2011' eur_date,
    @iso := '2011-01-01' iso_date,
    STR_TO_DATE(@eur, GET_FORMAT(DATE, 'EUR')) eur_str2date,
    STR_TO_DATE(@iso, GET_FORMAT(DATE, 'ISO')) iso_str2date,
    (@eur REGEXP '^[0-3][0-9]\.[01][0-9]\.20[0-9]{2}$') eur_valid_date,
    (@iso REGEXP '^20[0-9]{2}-[01][0-9]-[0-3][0-9]$') iso_valid_date,
    @date := @eur test_date,
    getSqlDate(@date) test_date_out;

/**
 * Output:
 * +------------+------------+--------------+--------------+----------------+----------------+------------+---------------+
 * | eur_date   | iso_date   | eur_str2date | iso_str2date | eur_valid_date | iso_valid_date | test_date  | test_date_out |
 * +------------+------------+--------------+--------------+----------------+----------------+------------+---------------+
 * | 01.01.2011 | 2011-01-01 | 2011-01-01   | 2011-01-01   |              1 |              1 | 01.01.2011 | 2011-01-01    | 
 * +------------+------------+--------------+--------------+----------------+----------------+------------+---------------+
 */

I agree with you. The code is written and tested in MySQL - thanks for asking. I've just added the info to the gist.