What are 1NF, 2NF and 3NF?
Understand the concept
Normalization organizes tables so each fact is stored in an appropriate place and changes do not create inconsistent copies. The first three normal forms progressively address repeating groups, dependence on only part of a key, and indirect dependence through other non-key facts. This reduces update, insert and delete anomalies.
Important ideas
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1NF: no repeating groups; values fit the chosen field structure.
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2NF: non-key fields depend on the whole candidate key, not only part of it.
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3NF: non-key facts do not depend on other non-key facts; separate department details from employees.
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Store department details in a department table rather than copying the department phone number onto every employee.
Can you explain it without the notes?
What are 1NF, 2NF and 3NF?
Use your own words. Explain an example and one limitation before checking the explanation.
Check your explanation
Normalization organizes tables so each fact is stored in an appropriate place and changes do not create inconsistent copies. The first three normal forms progressively address repeating groups, dependence on only part of a key, and indirect dependence through other non-key facts. This reduces update, insert and delete anomalies.
Turn this concept into a clear answer.
- Explain a concrete anomaly first; introduce denormalization only as a deliberate read-performance trade-off with a consistency plan.
Adapted from 05_SQL_POSTGRESQL.md · “What are 1NF, 2NF and 3NF?”. Examples are study fragments; framework behavior can depend on your version.