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3 Normal Forms in Relational Database Theory

7 February, 2011 at 2:58 pm Leave a comment

I find this guide easiest to understand:

First normal form (no items appear more than once)

1. each col must have a unique name
2. order of rows and cols doesn’t matter
3. each col must have a single data type
4. no 2 rows can contain identical values
5. each col must contain a single value
6. cols cannot contain repeating groups

Second normal form (primary key determine value of other columns)

1. in 1NF
2. all non-key fields depend on all of the key fields

Third normal form (value not determined by any non-primary key)

1. in 2NF
2. contains no transitive dependencies (when one non-key field’s value depends on another non-key field’s value)

Source: from Beginning Database Design Solutions (Rod Stephens)

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