| 1NF |
First Normal Form
"a relation" |
Any table that meets the definition of a relation:
- Single value cells (no repeating groups or arrays)
- Column (attribute) entry values are to be of the same kind for all instances
- Unique column (attribute) names
- No identical rows
- The order of columns and rows is not important
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| 2NF |
Second Normal Form
"every attribute depends on the key, the whole key" |
- All nonkey attributes are functionally dependent on the entire key.
- This is true for single attribute keys or composite keys.
- Therefore, no non-key attribute’s value can be determined by knowing just part of the primary key’s value.
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3NF
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Third Normal Form
"and nothing but the key" |
- Every non-key attribute must be non-transitivly depdendent on the primary key.
- Therefore, no non-key attribute’s value can be determined by knowing the value of another non-key attribute or set or non-key attributes.
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BCNF
|
Boyce-Codd Normal Form |
Every determinant is a candidate key.
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4NF
|
Fourth Normal Form |
No multi-value dependencies.
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5NF
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Fifth Normal Form |
Subrelations that cannot be reconstructed.
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DK/NF
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Domain/Key Normal Form |
Every constraint on the relation is a logical consequence of the definition of keys and domains.
- DKNF is not defined in terms of functional dependencies. DKNF is defined in terms of constraints, keys, and domains.
- A relation is in DKNF if every constraint can be logically derived from its keys and domains. In other words, once we appropriately define the keys and domains of the attributes, we can express all constraints on the relation.
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