Transcript Ch04r
Chapter 4: Database Management Data People Information Systems Hardware Telecommunications Software Databases Before the Use of Computers • Data kept in books, ledgers, card files, folders, and file cabinets • Long response time • Labor-intensive • Often incomplete or inaccurate Key Database Issues and Activities • Entering and Querying Data • Creating Database Reports • Maintaining Data Entering and Querying Data • Use a form for data entry • Use queries to retrieve information – Structured Query Language (SQL) – Query by example (QBE) Creating Database Reports • Report – A compilation of data organized and produced in printed format • DBMS packages include a report writer • Graphics can be added • Can be automatically updated by linking to data To Efficiently Maintain Data • Model the data • Select a physical structure – Hierarchical – Network – Relational • Normalization process – Incl. Update / insert / delete procedures Data Modeling • Ensures all needed data represented in the correct form, • Identifies all the relationships that exists among data: “Associations”, • Communicates assumptions about the data and relationships with the users of data. Associations • Relationships among the entities in the data structures • Three types – One-to-one – One-to-many – Many-to-many - U.S. Airways • The fifth largest airline in America, U.S. Airways--with 2500 jet flights per day--is using an IBM database system to better manage its in-flight meal and video services. By analyzing upgrade, noshow, and cancellation patterns, U.S. Airways can more accurately predict how many meals are needed on each flight. … (page 2-92) Selecting a physical structure in which to store the data • Hierarchical • Network • Relational The Hierarchical Model The Network Model The Relational Model Normalization • A technique used to make complex databases more efficient • Break one large table into several smaller tables – Eliminates all repeating groups in records – Eliminates redundant data Redundant Data Normalized Data Logical vs. physical representation of data • The same “number” can be: – An invoice number in sales – A billing number in accounting – A picking number in warehouse – A delivery ticket number in distribution Recent Developments • Databases and Client-Server Computing – Server holds the actual database – Clients hold software to work with the database Client/Server Database Recent Developments • Object-Oriented Databases (OODBs) – Treat tables, queries, etc., as reusable objects Recent Developments • Data Mining (On-Line Analytical Processing) – Drill down from summary data to detailed data – Data Warehouses/Data Marts • Integrates many large databases into one repository • Table 4.3 Sample industry uses of data warehousing (adapted from: Boar, 1998). Recent Developments • Linking Web Site Applications to Organizational Databases – Users have Web view to organizational database – Improves customer contact and service – Adds security as a concern - CNN Interactive • An example of successfully linking a large corporate database with a Web interface can be found at CNN Interactive. CNN Interactive provides a free, online custom news service to hundreds of thousands of subscribers around the world. … (page 2-109) Effective Management of Databases • Database Administrator (DBA) – Responsible for the development and management of an organization’s databases • Works with systems analysts on design • Works with users and managers on managerial and organizational issues • Responsible for implementing security features Key Terms • Databases: Collections of related data organized in a way that facilitates data searches. • Database management systems: Software applications with which you can create, store, organize, and retrieve data for one or many databases. • Entity: Things about which we collect data, such as people, courses, customers, or products. • Tables: Collections of related records about an entity type, where each row is a record and each column is a field. • Field: Individual pieces of information about an entity, such as a person’s last name or social security number, stored in a database cell. • Record: A collection of related fields about an entity, usually displayed as a row in a database. • Form: A collection of blank entry boxes, each representing a field, which is used to enter information into a database. • • Querying: Requesting information from a database. • • Structured Query Language (SQL): The most common set of commands used to request information from a database. • • Query by example (QBE): A capability of a DBMS to enable us to request data by simply providing a sample or a description of the types of data we would like to see. • Report: A compilation of data that is organized and produced in a printed format. • • Data model: A representation of entities and their relationships in the real world. • • Primary key: A field included in a database that can be used to uniquely identify each instance of an entity. • • Data type: Format for the data stored within a field. • Data dictionary: A repository that describes data types, uses, storage requirements, rules that affect data, and so on. • • Hierarchical database model: A DBMS approach in which entities are described in a parent-child relationship. • Network database model: A DBMS approach in which entities can have multiple parent-child relationships. • Relational database model: A DBMS approach in which entities are presented as twodimensional tables that can be joined together with common columns • • Normalization: A process of making data structures simple and clear • • Client/server architecture: A distributed processing system in which a client application that needs data or software gets it from a server that is a source for some or all of the needed data or software. • Database server: a powerful computer that contains the database and responds to queries from client computers in a client/server application. • • Object-oriented databases: Database management systems that follow the objectoriented approach of reusable objects, encapsulation, inheritance, and so on. • Data mining: Sorting and analyzing information stored in organizational databases • Data warehouses: Repositories integrating multiple large databases and other informational sources in a single repository or access point that is suitable for direct querying, analysis, or processing. • Data marts: Small-scale data warehouses that contain a sub-set of the data for a single aspect of a company’s business (for example, finance, inventory, or personnel). • Database administrator: Person responsible for the development and management of the organization’s databases.