Skilirium

6. etapp: Füüsilise andmemudeli kujundamine

Kompetentsi Andmete modelleerimine knobit · K-613 · Oskus

Recognises a referential action destroying what should survive

Mida see tähendab

`ON DELETE CASCADE` or `SET NULL` on a relationship whose child has a life of its own. A deletion anomaly made automatic: deleting one fact silently deletes or erases another.

Kuidas seda hinnatakse

Flags the deficient case and passes the acceptable one. Deficient: `fk_payment_account` with `on_delete: cascade`: purging a closed account deletes its payments and holds. `fk_payment_authorised_by` with `set null`: deleting a user erases who authorised the payment Acceptable: `on_delete: restrict` by default; `cascade` only for children that cannot exist without the parent (an instalment with its repayment schedule), with the data rule cited

Vajalik

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