MySQL Pivot Stored Procedure

mysql_pivot.sql

DROP PROCEDURE IF EXISTS pivot_user_preferences;

DELIMITER $$

CREATE PROCEDURE pivot_user_preferences(IN user_id INT)
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE definition_label CHAR(255);
    DECLARE label_cursor CURSOR FOR SELECT DISTINCT label FROM example_db.user_preferences;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    SET @user_id = user_id;
    SET @sql_statement = 'SELECT u.* ';

    OPEN label_cursor;

    read_loop: LOOP
        FETCH label_cursor INTO definition_label;
        IF done THEN
            LEAVE read_loop;
        END IF;
        SET @sql_statement = CONCAT(@sql_statement, ', GROUP_CONCAT(IF(up.label = \'', definition_label, '\', up.value, NULL)) AS ', definition_label);
    END LOOP;

    CLOSE label_cursor;

    SET @sql_statement = CONCAT(@sql_statement, ' FROM users u LEFT JOIN user_preferences up ON u.id = up.user_id WHERE u.id = (?) GROUP BY id');
    PREPARE stmt FROM @sql_statement;
    EXECUTE stmt USING @user_id;
    DEALLOCATE PREPARE stmt;
END $$

DELIMITER ;