What is the method for adding a non-null value to a many-to-many table?

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To add a non-null value to a many-to-many table, you need to create a new row in the table that contains the corresponding foreign key values for both sides of the relationship. For example, if you have a many-to-many relationship between orders and products, you would create a new row in the join table that includes the order ID and the product ID for the new product that you want to add to the order. This will establish a link between the order and the product and allow you to retrieve the complete list of products for the order or the complete list of orders for the product.