mysql string转int减法

SELECT product_price * CAST(quantity AS SIGNED) AS total_price
FROM orders
WHERE order_id = 123;

SELECT product_price * CAST(REPLACE(non_numeric_chars, 'quantity', '') AS SIGNED) AS total_price
FROM orders
WHERE order_id = 123;

SELECT product_price * CAST(quantity AS BIGINT) AS total_price
FROM orders
WHERE order_id = 123;

CREATE TABLE products (
    product_id INT PRIMARY KEY,
    product_name VARCHAR(255),
    product_price DECIMAL(10, 2),
    quantity VARCHAR(50)
);

INSERT INTO products (product_id, product_name, product_price, quantity)
VALUES (1, 'Product A', 10.50, '5'),
       (2, 'Product B', 20.75, '10');

SELECT product_name, product_price * CAST(quantity AS SIGNED) AS total_price
FROM products
WHERE product_id = 1;