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Types of Attributes

19 一月, 2016 - 14:28

There are a few types of attributes you need to be familiar with. Some of these are to be left as is, but some need to be adjusted to facilitate representation in the relational model. This first section will discuss the types of attributes. Later on we will discuss fixing the attributes to fit correctly into the relational model.

Simple attributes are attributes that are drawn from the atomic value domains

e.g. Name = {John} ; Age = {23} , also called Single valued. Composite attributes: Attributes that consist of a hierarchy of attributes

e.g. Address may consists of “Number”, “Street” and “Suburb” → Address = {59 + ‘Meek Street’ + ‘Kingsford’}

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Figure 8.3 Source: http://cnx.org/content/m28250/latest/  
 

Multivalued attributes: Attributes that have a set of values for each entity

e.g. Degrees of a person: ‘ BSc’ , ‘MIT’, ‘PhD’

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Figure 8.4 Source: http://cnx.org/content/m28250/latest/ 
 

Derived attributes: Attributes contain values that are calculated from other attributes

e.g. Age can be derived from attribute DateOfBirth. In this situation, DateOfBirth might be called Stored Attribute.

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Figure 8.5 Source: http://cnx.org/content/m28250/latest/