Storing Organizational Information - Databases

Relational Database Fundamentals

•Information is everywhere in an organization

•Information is stored in databases

–Database – maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses)

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•Database models include:

–Hierarchical database model – information is organized into a tree-like structure (using parent/child relationships) in such a way that it cannot have too many relationships

–Network database model – a flexible way of representing objects and their relationships

–Relational database model – stores information in the form of logically related two-dimensional tables

 Entities and Attributes

•Entity – a person, place, thing, transaction, or event about which information is stored

–The rows in each table contain the entities

–In Figure 7.1 CUSTOMER includes Dave’s Sub Shop and Pizza Palace entities

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•Attributes (fields, columns) – characteristics or properties of an entity class

–The columns in each table contain the attributes

–In Figure 7.1 attributes for CUSTOMER include Customer ID, Customer Name, Contact Name

 Keys and Relationships

•Primary keys and foreign keys identify the various entity classes (tables) in the database

–Primary key – a field (or group of fields) that uniquely identifies a given entity in a table

–Foreign key – a primary key of one table that appears an attribute in another table and acts to provide a logical relationship among the two tables