删除产品后如何继续使用交易中的数据

Question

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I have a problem regarding transaction data in the reports of products that have been sold. Constraints that occur if the product has entered the transaction / order but the product in question has been deleted.

How do I make the transaction report can still be used with the product that was deleted earlier?

Thanks.

Answer 1

Perhaps the best way to handle this possibility would be to add constraints to the tables involved which would make it not possible to delete a product row if an extant order exists which uses that product. Here is what the table definitions for Products and Order_Items might look like:

CREATE TABLE Order_Items (
    order_item_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    order_id INT NOT NULL,
    product_id INT NOT NULL,
    ...
    FOREIGN KEY fk_prod (product_id) REFERENCES Products (product_id)
)

CREATE TABLE Products (
    product_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    product_name VARCHAR(255) NOT NULL,
    ...
)

With this design in place, should someone attempt to delete a product record from the Products table while there exists on or more order item records referring to that product, the delete attempt would fail.

Answer 2

If a row in the Products table is used for two things, namely for purchasing the product and for reporting on a historical transaction, then you can never actually delete the row.

You might flag it in various ways: "available_for_purchase", "inventory = 0", "no_longer_produced", etc.