• The next higher level of the data hierarchy stores collections of fields known as records. By using a record that includes fields holding values for FirstName, LastName, Gender, and Age, you find that Bob Smith is a customer who is a 21-year- old male. At the next level up, the data hierarchy assembles records into a collection called a table or file. For instance, at this level you would find a set of records listing the age and gender of all customers, not just Bob Smith. Finally, the top level compiles the organized collection of files into a database. Using a database system to organize data provides several advantages: These advantages improve the accuracy of the data stored (data integrity), as well as increase its use. • The organization of the data is independent of any one software application. This allows all applications to access the data in a standard manner. • The organization of the data reduces data redundancy; a DBMS may need to store only one record of data for a particular product. • The DBMS can include features for maintaining the quality of the data, handling security, and synchronizing access by simultaneous users. • The database system allows for capabilities such as improved data access, allowing different views of the data for different users, and report generation.
Relational Data Model • In this method, known as the relational data model , databases store information about entities, such as suppliers and products for a retailer, and the relationships between those entities. Databases then use these defined relationships to store the connections between the entities, such as which suppliers provide which products. • The relational data model has since become the standard way of storing large amounts of data. Researchers at various universities and business organizations (notably University of California at Berkeley and IBM) developed systems based on Codd’s relational model. These systems are now known as relational database management systems (RDBMS). • The relational data model stores data in one or more tables, corresponding to entities. Tables consist of records, represented by the rows of the table. The records generally hold data about a single instance of an entity. Two types of models are commonly used to design the organization of relational database: • The entity-relationship diagram (ERD), which indicates the entities and how they are related • The logical data model translates the ERD into a diagram of the tables in the database • An entity is a noun, an object, which the information system keeps track of • Entities have attributes • Entities can be enduring (master data) or temporary (transaction data) o E.g. Product is enduring data, Purchase is temporary data (point in time) Storing and Accessing Data, Information, and Knowledge • Data Warehouses: A data warehouse is a means of storing and managing data for information access, typically composed of data from one or more transaction data- bases. It thus consists of transaction data, cleaned and restructured to fit the data
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