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21 Cards in this Set
- Front
- Back
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Terminologies of the relational model |
Relation Attribute Domain Tuple Degree Cardinality Relational database |
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RELATION |
A relation is a table with columns and rows |
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ATTRIBUTE |
An Attribute is a named column of a relation. |
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DOMAIN |
A Domain defines the permitted range of values for an attribute of an entity. |
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TUPLE |
A Tuple is a row of a relation. |
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DEGREE |
A Degree is the number of attributes a relation contains. |
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CARDINALITY |
Cardinality is the number of tuples a relation contains. |
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RELATIONAL DATABASE |
RD is a collection of normalized relations with distinct relation names. |
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Formal Terms |
Relation Tuple Attribute |
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Alternative 1 |
Table Row Column |
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Alternative 2 |
File Record Field |
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Properties of Database Relations |
Each attribute has a distinct name. Each cell of the relation contains exactly one atomic value.. The relation has a name distinct from all other relation names in the relational schema. Each tuple is distinct; there are no duplicate tuples The values of an attribute are all from the same domain. |
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SUPER KEY |
Is an attribute or set of attributes that uniquely identifies a tuple within a relation |
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CANDIDATE KEY |
Is a subset of the super key that can uniquely identify other attributes of the table. |
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COMPOSITE KEY |
Is a combination of two or more columns in a table. |
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PRIMARY KEY |
Is a collection of columns that contain values that uniquely identify each row in a table. |
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ALTERNATE KEY |
Refers to the candidate keys that are not selected to be the primary key. |
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FOREIGN KEY |
Is a column or combination of columns that is used to establish a link between the data in two tables. |
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Integrity Rules |
Entity Integrity Referential Integrity |
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Entity Integrity |
Requires that no attribute of a primary key can be null. |
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Referential Integrity |
Is the logical dependency of a foreign key on a primary key. |
