Computed column using variables shows invalid values

CREATE TABLE `products` (

  `product_id` INT,

  `code` VARCHAR(24),

  `price` DECIMAL(10,2),

  `avgOrderQuantity` INT

);

CREATE TABLE `orders` (

  `order_id` INT,

  `date` DATETIME DEFAULT CURRENT_TIMESTAMP,

  `state` ENUM('pending','confirmed','cancelled','completed')

);

CREATE TABLE `order_products` (

  `order_id` INT,

  `product_id` INT,

  `quantity` INT,

  `price` DECIMAL(10,2)

);

CREATE TABLE `invoices` (

  `invoice_id` INT,

  `order_id` INT,

  `date` DATETIME DEFAULT CURRENT_TIMESTAMP

);

CREATE TABLE `invoice_products` (

  `invoice_id` INT,

  `product_id` INT,

  `quantity` INT,

  `price` DECIMAL(10,2)

);

--

INSERT INTO `products` (`product_id`, `code`, `price`, `avgOrderQuantity`) VALUES

(1, 'COD1', 12, 3), (2, 'COD2', 11, 1);

INSERT INTO `orders` (`order_id`, `state`) VALUES

(1, 'confirmed'),

(2, 'confirmed'),

(3, 'pending');

INSERT INTO `order_products` (`order_id`, `product_id`, `quantity`, `price`) VALUES

(1, 1, 30, 10.2),

(2, 1, 10, 12), (2, 2, 2, 11),

(3, 1, 10, 12);

INSERT INTO `invoices` (`invoice_id`, `order_id`) VALUES

(1, 1),

(2, 2),

(3, 1);

INSERT INTO `invoice_products` (`invoice_id`, `product_id`, `quantity`, `price`) VALUES

(1, 1, 10, 10.2),

(2, 1, 20, 12), (2, 2, 2, 11),

(3, 1, 1, 10.2);

  SELECT

    P.code,

    O.state,

    @ordered := OP.quantity AS ordered,

    @invoiced := IFNULL((

      SELECT SUM(IP.quantity)

      FROM invoices AS I

        LEFT JOIN invoice_products AS IP

          ON IP.invoice_id = I.invoice_id

      WHERE I.order_id = O.order_id

        AND IP.product_id = OP.product_id

    ), 0) AS invoiced,

    @sold := IF(O.state = 'confirmed', @ordered, @invoiced) AS sold,

    @avgOrdQty := P.avgOrderQuantity AS avgOrdQty,

    IF(@sold > @avgOrdQty, @avgOrdQty, @sold) AS avgSold

  FROM order_products AS OP

    INNER JOIN orders AS O

      ON O.order_id = OP.order_id

    INNER JOIN products AS P

      ON P.product_id = OP.product_id

  WHERE O.state != 'pending';

SELECT T.code, SUM(T.avgSold)

FROM (

  SELECT

    P.code,

    O.state,

    @ordered := OP.quantity AS ordered,

    @invoiced := IFNULL((

      SELECT SUM(IP.quantity)

      FROM invoices AS I

        LEFT JOIN invoice_products AS IP

          ON IP.invoice_id = I.invoice_id

      WHERE I.order_id = O.order_id

        AND IP.product_id = OP.product_id

    ), 0) AS invoiced,

    @sold := IF(O.state = 'confirmed', @ordered, @invoiced) AS sold,

    @avgOrdQty := P.avgOrderQuantity AS avgOrdQty,

    IF(@sold > @avgOrdQty, @avgOrdQty, @sold) AS avgSold

  FROM order_products AS OP

    INNER JOIN orders AS O

      ON O.order_id = OP.order_id

    INNER JOIN products AS P

      ON P.product_id = OP.product_id

  WHERE O.state != 'pending'

) AS T

GROUP BY T.code;