Data Deletion

Safely and effectively removing data from a system while maintaining audit trails, data integrity, and compliance.

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🧩 Overview

Data Deletion refers to the intentional removal of records from a database. This process must be handled with care to:

• Prevent accidental data loss
• Ensure traceability and audit compliance
• Respect data retention and privacy policies
• Avoid breaking relational integrity

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🧯 Types of Deletion

Type	Description
Hard Delete	Physically removes data from the database
Soft Delete	Flags data as deleted (e.g., is_deleted = true)
Cascade Delete	Automatically deletes related data via constraints
Conditional Delete	Removes records only under specific criteria

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🔄 Deletion Workflow

User Action → Validation & Confirmation → Soft/Hard Delete → Log Audit → Return Response

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🧪 Example: Hard Delete Query

DELETE FROM patients WHERE id = 105;

🔥 Use only when permanent deletion is required and confirmed.

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🌥️ Example: Soft Delete Query

UPDATE patients SET is_deleted = 1, deleted_at = NOW() WHERE id = 105;

🛡 Recommended for audit compliance and reversible recovery.

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⚙️ Backend Implementation

API (Express.js Example)

router.delete("/patients/:id", async (req, res) => {
  const id = req.params.id;
  await db.query("UPDATE patients SET is_deleted = 1 WHERE id = ?", [id]);
  res.json({ status: "deleted" });
});

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✅ Validation & Safety

Before performing deletion:

• Confirm identity or permissions of the user
• Check for dependencies in related tables
• Prompt confirmation dialogs in UI
• Optionally require reason for deletion

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🔗 Referential Integrity

To avoid breaking references:

• Use ON DELETE CASCADE when child records must be removed:

  FOREIGN KEY (patient_id) REFERENCES patients(id) ON DELETE CASCADE
• Use ON DELETE SET NULL when links must be preserved but disassociated

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🕵️‍♂️ Audit Trail

Log deletion metadata:

{
  "action": "delete",
  "entity": "patients",
  "entity_id": 105,
  "deleted_by": "admin",
  "deleted_at": "2025-05-22T09:45:00Z",
  "reason": "Duplicate record"
}

Store this in a dedicated audit_log or deletion_log table.

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📜 Compliance Considerations

• Ensure deletion complies with policies like GDPR or HIPAA
• Provide users ability to request data deletion
• Maintain data retention schedules
• For sensitive deletions, implement two-step approval

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🧩 UI Suggestions

• Add Delete button with:
  • Warning dialog
  • Option to undo (if soft deleted)
  • Optional reason input
• Highlight soft-deleted records with a badge (e.g., "Archived")

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🧠 Best Practices

• Prefer soft delete unless legal removal is required
• Backup data before irreversible deletes
• Use transactions for bulk deletions
• Index the is_deleted field for faster lookups
• Hide soft-deleted data from listings by default:

  SELECT * FROM patients WHERE is_deleted = 0;

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🔚 Summary

Data Deletion is more than just a DELETE query — it is a controlled, auditable process designed to protect both the system and its users. Always balance safety, transparency, and performance.

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