Glossary 1st (Web server extensions) Normal Form (1NF) Eliminate repeating groups, such
January 9th, 2008Glossary 1st Normal Form (1NF) Eliminate repeating groups, such that all records in all tables can be identified uniquely, by a primary key in each table. In other words, all fields other than the primary key must depend on the primary key. All Normal Forms are cumulative. (See Normal Forms.) 1st Normal Form made easy Remove repeating fields by creating a new table, where the original and new tables are linked together with a master-detail, one-to-many relationship. Create primary keys on both tables, where the detail table will have a composite primary key, containing the master table primary key field as the prefix field of its primary key. That prefix field is also a foreign key back to the master table. 2nd Normal Form (2NF) All non-key values must be fully functionally dependent on the primary key. No partial dependencies are allowed. A partial dependency exists when a field is fully dependant on a part of a composite primary key. All Normal Forms are cumulative. (See Normal Forms.) 2nd Normal Form made easy Performs a seemingly similar function to that of 1st Normal Form, but creates a table, where repeating values (rather than repeating fields) are removed to a new table. The result is a many-to-one relationship rather than a one-to-many relationship (see 1st Normal Form), created between the original (master table) and the new tables. The new table gets a primary key consisting of a single field. The master table contains a foreign key pointing back to the primary key of the new table. That foreign key is not part of the primary key in the original table. 3rd Normal Form (3NF) Eliminate transitive dependencies. What this means is that a field is indirectly determined by the primary key because the field is functionally dependent on another field, where the other field is dependent on the primary key. All Normal Forms are cumulative. (See Normal Forms.) 3rd Normal Form made easy Elimination of a transitive dependency, which implies creation of a new table, for something indirectly dependent on the primary key in an existing table. 4th Normal Form (4NF) Eliminate multiple sets of multi-valued dependencies. All Normal Forms are cumulative. (See Normal Forms.)
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