How do foreign keys help, and when can cascade delete be risky?

Use foreign keys and cascade rules safely

Explains referential integrity, cascade delete trade-offs, restrict behavior, soft deletes, and operational safety.

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Foreign keys enforce that related rows point to valid parent rows. They protect data integrity even if a bug or manual operation bypasses application code. Cascade delete can be convenient for tightly owned child rows, such as order draft items deleted with a draft. It becomes risky when the child data has audit, billing, history, or retention meaning. In those cases I would use restrict, soft delete, or an explicit cleanup workflow.

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Referential integrity, cascading deletes, restrict rules, soft delete, data retention, and cleanup workflows.

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Foreign keys are basic on the surface, but the trade-offs become real when products delete accounts, tenants, files, and history.
Foreign keys enforce that related rows point to valid parent rows. They protect data integrity even if a bug or manual operation bypasses application code. Cascade delete can be convenient for tightly owned child rows, such as order draft items deleted with a draft. It becomes risky when the child data has audit, billing, history, or retention meaning. In those cases I would use restrict, soft delete, or an explicit cleanup workflow.
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I would choose cascade rules based on ownership and business lifetime. If a child cannot exist without the parent and has no independent meaning, cascade may be fine. If deleting a parent could remove important history, I would block deletion or mark records inactive. Soft deletes need careful uniqueness, filtering, and reporting behavior. The database constraints and application behavior need to agree.

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Using cascade delete everywhere because it is convenient.
Removing audit or billing history accidentally.
Soft deleting rows without updating uniqueness and filters.
Ignoring performance of large cascades.

How do foreign keys help, and when can cascade delete be risky?

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