Term
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Definition
Represented by a rectangle and labeled with a singular noun
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Term
| Entity Crows Foot Notation |
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Definition
| Represented by a rectangle and labeled with a singular noun |
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Term
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Definition
| Properties or characteristics of entities |
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Term
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Definition
| Represented by ovals connected to entity rectangle with a line |
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Term
| Attribute Crows Foot Notation |
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Definition
| Written in the attribute box |
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Term
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Definition
Required
Optional
Identifies
Composite Identifiers |
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Term
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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
| One or more attributes that uniquely identify each entity instance |
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Term
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Definition
| Primary key composed of more than one attribute |
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Term
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Definition
Can be subdivided
Never use |
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Term
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Definition
Cannot be subdivided
Only one value |
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Term
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Definition
| Can have only a single value |
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Term
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Definition
Can have many values
Phone number
Not allowed in relational models |
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Term
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Definition
Value may be calculated from other attributes
Need not be physically stored in the database
DOB |
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Term
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Definition
| Entities that participate in a relationship |
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Term
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Definition
Describes the relationship classification
1:1
1:N
M:N |
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Term
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Definition
| Expresses minimum and maximum number of entity occurrences associated with one occurrence of related entity |
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Term
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Definition
| Entity exists in database only when it is associated with another related entity occurrence |
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Term
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Definition
Entity can exist apart from one or more related entities
Sometimes such an entity is referred to as a strong or regular entity |
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Term
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Definition
Weak (non-identifying) relationship
Strong (identifying) relationship |
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Term
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Definition
Non Identifying Relationship
Entity is existence dependent
Primary key partially or totally derived from parent entity in relationship |
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Term
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Definition
Identifying Relationship
Exists when PK of related entity contains PK component of parent entity |
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Term
| Relationship Participation |
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Definition
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Term
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Definition
One entity occurrence does not require corresponding entity occurrence in particular relationship
May
Circle
Minimum number of related records is 0 |
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Term
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Definition
One entity occurrence requires corresponding entity occurrence in particular relationship
Must
Line
Minimum number of related records is 1 |
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Term
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Definition
Represents the number of entities or participants associated with a relationship
Unary Relationship
Binary Relationship
Ternary Relationship |
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Term
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Definition
Recursive Relationship
Association is maintained within single entity |
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Term
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Definition
| Two entities are associated |
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Term
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Definition
| Three entities are associated |
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