Normalization

One wide table stores the same fact over and over — until an update misses a copy. Follow the functional dependencies as the table splits into 1NF, 2NF, 3NF and BCNF.

Functional dependencies

Lossless splits

Each fact stored once

Table

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Step 1 of 0

TableAnomalies1NF2NF3NFBCNFResult

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The Normal Forms

1NF

Every cell holds one atomic value.

2NF

No non-prime attribute may depend on only part of a candidate key.

3NF

For every dependency X → A, X is a superkey or A is prime (part of some key).

BCNF

For every dependency X → A, X is a superkey. No exceptions.

Each form implies the ones before it. A prime attribute belongs to at least one candidate key; a superkey determines every column of its table.

Knowledge Check

Question 1 of 3

A table has key {StudentID, CourseID} and the dependency StudentID → Name. Which normal form does it break?

DSAverse

Normalization

The Normal Forms

Knowledge Check

See also

Normalization

The Normal Forms

Knowledge Check

See also