Question

Which specific database normalization form ensures that a table has no partial dependencies of non-key attributes on a composite primary key?

Accepted Answer

The specific database normalization form that ensures a table has no partial dependencies of non-key attributes on a composite primary key is Second Normal Form (2NF). A table must first satisfy the conditions of First Normal Form (1NF) before it can be in 2NF. A table is in First Normal Form (1NF) if all its attribute values are atomic, meaning each cell contains a single value and there are no repeating groups of columns. For example, a single cell should not contain a list of items or multiple values. Once a table is in 1NF, the next step is to ensure it meets the requirements for 2NF. A composite primary key is a primary key that consists of two or more attributes (columns) whose values, when combined, uniquely identify each row in a table. For instance, in an `OrderItems` table, `(OrderID, ProductID)` could serve as a composite primary key. A non-key attribute is any attribute in a table that is not part of the primary key. A partial dependency occurs when a non-key attribute is functionally dependent on only a part of a composite primary key, rather than on the entire composite primary key. This means that a segment of the primary key is sufficient to determine the value of a non-key attribute. For example, if a table has a composite primary key `(OrderID, ProductID)` and also contains `ProductName` and `OrderDate` as non-key attributes: `ProductName` might only depend on `ProductID` (e.g., `ProductID` uniquely determines `ProductName`), which is only a part of the composite primary key. Similarly, `OrderDate` might only depend on `OrderID`. Both are examples of partial dependencies. Second Normal Form (2NF) ensures that a table is in 1NF and all its non-key attributes are fully functionally dependent on the entire primary key. This condition explicitly eliminates partial dependencies. Full functional dependency means that a non-key attribute is dependent on the *entirecomposite primary key and cannot be determined by any proper subset of that primary key. To achieve 2NF, any non-key attributes that are partially dependent on a part of the composite primary key must be moved to a new table where that part of the composite key becomes the new table&#x27;s primary key. By removing these partial dependencies, 2NF ensures that every non-key attribute describes the whole entity identified by the entire primary key, thereby directly addressing and resolving the issue of partial dependencies.

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Which specific database normalization form ensures that a table has no partial dependencies of non-key attributes on a composite primary key?