Data Basing 101

1942 words 8 pages
Conceptual Data Models for Database Design

Database Design Process

The database design process consists of a number of steps listed below. We will focus mainly on step 2, the conceptual database design, and the models used during this step.

Step 1: Requirements Collection and Analysis ▪ Prospective users are interviewed to understand and document data requirements ▪ This step results in a concise set of user requirements, which should be detailed and complete. ▪ The functional requirements should be specified, as well as the data requirements. Functional requirements consist of user operations that will be applied to the database, including retrievals and updates. ▪ Functional requirements can be documented using
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For these situations, the value null is created. ▪ A person who does not have a mobile phone would have null stored at the value for the Mobile Phone Number attribute. ▪ Null can also be used in situations where the attribute value is unknown. There are two cases where this can occur, one where it is known that the attribute is valued, but the value is missing, for example hair color. Every person has a hair color, but the information may be missing. Another situation is if mobile phone number is null, it is not known if the person does not have a mobile phone or if that information is just missing.

Complex Attributes

▪ Complex attributes are attributes that are nested in an arbitrary way. ▪ For example a person can have more than one residence, and each residence can have more than one phone, therefore it is a complex attribute that can be represented as: ▪ {Multi-valued attributes are displayed between braces} ▪ (Complex Attributes are represented using parentheses)

E.g.
{AddressPhone({Phone(AreaCode, PhoneNumber)}, Address(StreetAddress(Number, Street, ApartmentNumber), City, State, Zip))}

Entity Types, Entity Sets, Keys and Value Sets

Entity Types and Entity Sets

▪ An entity type defines a collection of entities that have the same attributes. Each entity type in the database is described by its name and attributes. The entity share the same attributes, but each entity has its own value for each

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