Modern Database Management - Chapter 4 Flashcards

Flashcards for reviewing Modern Database Management Chapter 4

Relation

A named, two-dimensional table of data consisting of rows (records) and columns (attributes or fields). Must have a unique name, atomic attribute values, unique rows, unique attribute names, and irrelevant column and row order.

Primary Keys

Unique identifiers of a relation, ensuring all rows are unique.

Foreign Keys

Identifiers that enable a dependent relation to refer to its parent relation.

Domain Constraints

Allowable values for an attribute, including data types and restrictions on values.

Entity Integrity

States that no primary key attribute may be null, ensuring all primary key fields contain data values.

Referential Integrity

Rules that maintain consistency between the rows of two related tables.

Restrict Delete Rule

Don’t allow delete of “parent” side if related rows exist in “dependent” side.

Cascade Delete Rule

Automatically delete “dependent” side rows that correspond with the “parent” side row to be deleted.

Set-to-Null Delete Rule

Set the foreign key in the dependent side to null if deleting from the parent side, not allowed for weak entities.

Well-Structured Relations

Relations that contain minimal data redundancy and allow users to insert, delete, and update rows without causing data inconsistencies.

Insertion Anomaly

Adding new rows forces user to create duplicate data.

Deletion Anomaly

Deleting rows may cause a loss of data that would be needed for other future rows.

Modification Anomaly

Changing data in a row forces changes to other rows because of duplication.

Functional Dependency

The value of one attribute (the determinant) determines the value of another attribute.

Candidate Key

A unique identifier for a record.

First Normal Form (1NF)

No multivalued attributes; every attribute value is atomic

Second Normal Form (2NF)

1NF plus every non-key attribute is fully functionally dependent on the ENTIRE primary key; no partial functional dependencies.

Third Normal Form (3NF)

2NF PLUS no transitive dependencies (functional dependencies on non-primary-key attributes).

View Integration

Combining entities from multiple E-R models into common relations.

Synonyms (in merging relations)

Two or more attributes with different names but same meaning.

Homonyms (in merging relations)

Attributes with same name but different meanings.