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- Superkey abstract "A superkey is defined in the relational model of database organization as a set of attributes of a relation variable for which it holds that in all relations assigned to that variable, there are no two distinct tuples (rows) that have the same values for the attributes in this set. Equivalently a superkey can also be defined as a set of attributes of a relation schema upon which all attributes of the schema are functionally dependent.Note that the set of all attributes is a trivial superkey, because in relational algebra duplicate rows are not permitted.Also note that if attribute set K is a superkey of relation R, then at all times it is the case that the projection of R over K has the same cardinality as R itself.Informally, a superkey is a set of attributes within a table whose values can be used to uniquely identify a tuple. A candidate key is a minimal set of attributes necessary to identify a tuple; this is also called a minimal superkey. For example, given an employee schema consisting of the attributes employeeID, name, job, and departmentID, we could use the employeeID in combination with any or all other attributes of this table to uniquely identify a tuple in the table. Examples of superkeys in this schema would be {employeeID, Name}, {employeeID, Name, job}, and {employeeID, Name, job, departmentID}. The last example is known as trivial superkey, because it uses all attributes of this table to identify the tuple.In a real database we do not need values for all of those attributes to identify a tuple. We only need, per our example, the set {employeeID}. This is a minimal superkey—that is, a minimal set of attributes that can be used to identify a single tuple. Therefore, employeeID is a candidate key.".
- Superkey wikiPageExternalLink 2.1.2_Keys.html.
- Superkey wikiPageID "1137952".
- Superkey wikiPageLength "4212".
- Superkey wikiPageOutDegree "18".
- Superkey wikiPageRevisionID "706160082".
- Superkey wikiPageWikiLink Candidate_key.
- Superkey wikiPageWikiLink Cardinality_(data_modeling).
- Superkey wikiPageWikiLink Category:Data_modeling.
- Superkey wikiPageWikiLink Compound_key.
- Superkey wikiPageWikiLink Database.
- Superkey wikiPageWikiLink Foreign_key.
- Superkey wikiPageWikiLink Functional_dependency.
- Superkey wikiPageWikiLink Projection_(relational_algebra).
- Superkey wikiPageWikiLink Relation_(database).
- Superkey wikiPageWikiLink Relational_algebra.
- Superkey wikiPageWikiLink Relational_model.
- Superkey wikiPageWikiLink Set_(mathematics).
- Superkey wikiPageWikiLink Tuple.
- Superkey wikiPageWikiLink Unique_key.
- Superkey wikiPageWikiLinkText "Superkey".
- Superkey wikiPageWikiLinkText "super key".
- Superkey wikiPageWikiLinkText "superkey".
- Superkey wikiPageUsesTemplate Template:About.
- Superkey wikiPageUsesTemplate Template:Cite_book.
- Superkey wikiPageUsesTemplate Template:Databases.
- Superkey wikiPageUsesTemplate Template:Refimprove.
- Superkey wikiPageUsesTemplate Template:Reflist.
- Superkey subject Category:Data_modeling.
- Superkey comment "A superkey is defined in the relational model of database organization as a set of attributes of a relation variable for which it holds that in all relations assigned to that variable, there are no two distinct tuples (rows) that have the same values for the attributes in this set.".
- Superkey label "Superkey".
- Superkey sameAs Q2068684.
- Superkey sameAs スーパーキー.
- Superkey sameAs 슈퍼_키.
- Superkey sameAs m.049jyk.
- Superkey sameAs Суперключ.
- Superkey sameAs Суперключ.
- Superkey sameAs Q2068684.
- Superkey wasDerivedFrom Superkey?oldid=706160082.
- Superkey isPrimaryTopicOf Superkey.