Normalisation: functional dependencies, 1NF and 2NF
50 min · Intermediate
Normalisation is splitting a badly designed table into smaller, well-linked tables so each fact is stored exactly once. It removes the anomalies that come from repeated data, and it is the most asked DBMS theory topic in placement interviews after keys.
Topics in this lesson
- Insert, update and delete anomalies
- Functional dependencies and attribute closure
- 1NF: atomic values
- 2NF: removing partial dependencies
- Worked decomposition example
Interview questions this lesson answers
- What is normalisation?
- Why do we normalise a database?
- What is an update anomaly?
- What is an insert anomaly?
- What is a delete anomaly?
- What is a functional dependency?
- What is a trivial functional dependency?
- What are Armstrong's axioms?
- What is attribute closure?
- How do you use closure to find a candidate key?
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