- the relationship between the "Product" and "Product_Category" entities is one-to-many.
2.There are two ways to ensure that each product in the "Product" table has a valid category assigned to it:
Add a foreign key constraint: A foreign key constraint is a database rule that ensures the data integrity between two tables. In this case, you could add a foreign key constraint to the "category_id" column in the "Product" table. This foreign key would reference the primary key ("id") of the "Product_Category" table. This would prevent products from being created with invalid category IDs.
Make the "category_id" column in the "Product" table NOT NULL: Setting the "category_id" column to NOT NULL would prevent products from being created without a category assigned to them. However, this approach would allow products to be assigned invalid category IDs.