Automatically converts a column to enum type, getting the values from the column itself

convert_to_enum.mysql

-- usage: CALL convert_to_enum('my_table', 'my_column');
DELIMITER $$
CREATE PROCEDURE `convert_to_enum`(IN tablename TEXT, IN colname TEXT)
BEGIN
    SET @temp = CONCAT(
        "SELECT CONCAT(\"ENUM('\", GROUP_CONCAT(DISTINCT ",
        colname,
        " ORDER BY ",
        colname,
        " SEPARATOR \"', '\"), \"')\") INTO @temp FROM ",
        tablename
    );

    PREPARE stmt FROM @temp; EXECUTE stmt; DEALLOCATE PREPARE stmt;

    SET @temp = CONCAT('ALTER TABLE ', tablename, ' MODIFY COLUMN ', colname, ' ', @temp, ';');

    PREPARE stmt FROM @temp; EXECUTE stmt; DEALLOCATE PREPARE stmt;
END$$
DELIMITER ;