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Database Design

Structure your data correctly — normalization reduces redundancy and prevents anomalies

Normalization 1NF / 2NF / 3NF Anomaly Prevention Schema Design
Unnormalized
→
1NF
→
2NF
→
3NF
75%
Redundancy Score
High — many duplicated values
0
JOIN Operations Needed
No joins — all in one table
1
Number of Tables
Single denormalized table

Key Concepts

🎯 When to Normalize
  • OLTP systems (transactional)
  • Data integrity is critical
  • Frequent UPDATE operations
  • Storage space is constrained
⚖️ Trade-offs
  • More joins = slower read queries
  • Denormalize for read-heavy OLAP
  • 3NF is usually the right target
  • BCNF / 4NF rarely needed in practice
🎓 Interview Tips
  • Name the 3 anomalies: update, insert, delete
  • 1NF: atomic values, no repeating groups
  • 2NF: no partial dependency (composite PK)
  • 3NF: no transitive dependency