Term
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Definition
| Collection of entities (persons, places, events, or things) of interest represented by a rectangle in an entity relationship diagram |
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Term
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Definition
| Property of an entity type or relationship; each one has a data type that defines the kind of values and permissible operations on the attribute |
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Term
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Definition
| Named associations among entity types; represents two-way or bidirectional association among entities; most involve 2 distinct entity types |
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Term
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Definition
| Constraint on the number of entities that participate in a relationship; minimum and maximum ones are specified for both directions of a relationship |
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Term
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Definition
| Minimum cardinality of one or more |
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Term
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Definition
| An entity that cannot exist unless another related entity exists; mandatory relationship |
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Term
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Definition
| Minimum cardinality of zero |
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Term
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Definition
| Maximum cardinality of one |
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Term
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Definition
| Maximum cardinality of more than one in both directions |
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Term
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Definition
| Maximum cardinality equals one in both directions |
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Term
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Definition
| An entity type that borrows all or part of its primary key from another entity type; identifying relationships indicate the entity types that supply components of the borrowed primary key |
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Term
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Definition
| Relationship that provides a component of the primary key |
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Term
| Identification Dependency |
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Definition
| Occurs because some entities are closely associated with other entities |
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Term
| Self Referencing Relationship |
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Definition
| Relationship involving the same entity type; represent associations among members of the same set; sometimes called reflective relationships |
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Term
| M-way (Multiway) Relationships |
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Definition
| Relationship can be connected to more than two entity types and is denoted by a diamond for relationships |
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Term
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Definition
| An M-way relationship involving three entity types |
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Term
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Definition
| A weak entity that depends on two or more entity types for its primary key; if it has more than 2 identifying relationships is is known as an M-way associative entity type |
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Term
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Definition
| M-N relationship can be replaced by an associative entity type and two identifying 1-M relationships; in most cases between a M-N relationship and the associative entity type is personal preference |
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Term
| Generalization Hierarchies |
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Definition
| A collection of entity types arranged in a hierarchical structure to show similarity in attributes. Each subtype or child entity type contains a subset of entities of its supertype or parent entity type |
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Definition
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Term
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Definition
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Term
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Definition
| A data modeling feature that supports sharing of attributes between a supertype and a subtype |
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Term
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Definition
| Subtypes in a generalization hierarchy do not have any entities in common |
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Term
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Definition
| Every entity of a supertype must be an entity in one of the subtypes in the generalization hierarchy |
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