Final exam review materials.docx - Week1(Basic concepts ERD...

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Week1(Basic concepts; ERD; Relational Database; BR; Entity;Atrributes; relationships)1.Traditional file processing system creates duplicate data2.Disadvantage of file processing Program-data dependence (all programs maintain metadata for each file they use)Duplication of dataDifferent systems/programs have separate copies of the same dataLimited data sharingNo centralized control of dataLengthy development times漫长的开发过程Excessive过度的 program maintenance80% of information systems budget3.Programs with data dependency(数据依赖性)Each application programmer must maintain his/her own data. Each application program needs to include code for the metadata of each fileEach application program must have its own processing routines for reading, inserting,updating, and deleting data. Lack of coordination and central controlNon-standard file formats4.Waste of space to have duplicate dataCauses more maintenance headaches棘手之事The biggest problem:Data changes in one file could cause inconsistenciesCompromises in data integrity 数据完整性的妥协5.Problem with spreadsheets: redundancyIn a spreadsheet, each row is intended to stand on its own. As a result, the same information may be entered several times6.The problem of storing redundant data Delete: some but not all instance of data Update: some but not all instance of dataInsert: multiple data entry can introduce inconsistency Multiple data entry is expensive. 7.Solution: the database approachCentral repository仓库 of shared data Data is managed by a controlling agent Stored in a standardized, convenient form8.Database management systemA software system that is used to define, create, maintain a database, and provide controlledaccess to user databases 9.Advantage of the database approach Program-data independence Planned data redundancy 1
Improved data consistency Improved data sharing Increased application development productivity Enforcement of standards Improved data quality Improved data accessibility and responsiveness 响应能力Reduced program maintenanceImproved decision support 10.Costs and risks of the database approach New, specialized personnel Installation and management cost and complexity Conversion costs Need for explicit backup and recovery Organizational conflict11.Components of the database environment Data modelling and design tools: automated tools used to design databases and applicationprograms Repository -centralized storehouse of metadata Database management system – software for managing the database Database – storehouse of the data Application programs- software using the data User interface- text, graphical displays, menus, etc, for userData/database administrators- personal responsible for maintaining the database System developers- personal responsible for designing databases and softwareEnd users: people who use the application and databases.

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