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25 Cards in this Set
- Front
- Back
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Relation
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A named two-dimensional table of data
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Primary Key
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An attribute ( or combination of attributes) that uniquely identifies each row in a relation
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Composite Key
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A primary key that consists of more than one attribute
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Foreign Key
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An attribute in a relation that serves as the primary key of another relation in the same database
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Null
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A value that may be assigned to an attribute when no other value applies or when the applicable value is unknown
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Entity Integrity Rule
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No primary key attribute ( or component of a composite primary key) may be null
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Referential Integrity Constraint
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A rule that sates that either each foreign key value must match a primary key value in another relation or the foreign value must be null
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Well-Structured Relation
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A relation that contains minimal redundancy and allows users to insert, modify, and delete the rows in a table without errors or inconsistencies
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Anomaly
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An error or inconsistency that may result when a user attempts to update a table that contains redundant data. Three types of anomalies are insertion, deletion, and modification
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Surrogate Primary key
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a serial number of other system assigned primary key for a relation
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Recursive Foreign Key
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A foreign key in a relation that references the primary key values of that same relation
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Normalization
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The process of decomposing relations with anomalies to produce smaller, well-structured relations
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Normal Form
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A state of a relation that results from applying simple rules regarding functional dependencies for relationships between attributes to that relation
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Functional Dependency
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A constraint between two attributes in which the value of one attribute is determined by the value of another attribute
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Determinant
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The attribute on the left-hand side of the arrow in a functional dependency
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Candidate Key
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An attribute, or combination of attributes, that uniquely identifies a row in a relation
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First Normal Form (1NF)
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A relation that has a primary key and in which there are no repeating groups
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Second Normal Form (2NF)
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A relation in first normal form in which every nonkey attribute is fully functionally dependent on the primary key
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Partial Functional Dependency
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A functional dependency in which one or more nonkey attributes are functionally dependent on part (but not all) of the primary key.
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Third Normal Form (3NF)
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A relation that is in second normal form and has no transitive dependencies
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Transitive Dependency
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A functional dependency between two (or more) nonkey attributes
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Synonyms
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Two (or more) attrubytes having different names but the same meaning, as when they describe the same characteristic of an entity.
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Alias
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An alternative name used for an attribute
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Homonym
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An attribute that may have more than one meaning
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Enterprise Key
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A primary key whose value is unique across all relations
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