ExamMid09discussion

ExamMid09discussion - Analysis of Midterm-Examination 1(5 Describe the working process with a database system a database definition By the database

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Sept. 2009 ACS-3902 Yangjun Chen 1 Analysis of Midterm-Examination 1.(5) Describe the working process with a database system. a) database definition By the database definition, we create an entity-relationship diagram for a realistic world problem, which is then transformed into a database schema. b) populating tables with data The second phase is the database construction, by which a database is initially populated with data. c) database manipulation Once a database is constructed, one can conduct some operation on it, such as data insertion, data deletion and data updating, which changes the database from a state to another state. It is the responsibility of a database system to guarantee that the database goes from one correct state to another.
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Sept. 2009 ACS-3902 Yangjun Chen 2 Analysis of Midterm-Examination 2.(10) Describe the three-schema architecture of a database system and the main functionality of each level in this architecture. a) internal level The first level is the internal level, which possesses an internal schema. It describes the physical storage structure of the database. The internal schema uses a physical data model and describes the complete details of data storage and access paths for the database. b) conceptual level The second level is the conceptual level, which has a conceptual schema. It describes the structure of the whole database for a community of users. The conceptual level hides the details of physical structures and concentrates on entity types, data types, relationships, user operations, and constraints. A high level data model or an implementation data model can be used at this level.
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Sept. 2009 ACS-3902 Yangjun Chen 3 Analysis of Midterm-Examination c) external level The third level is the so-called external level or the view level, which includes a number of external schemas or user views. It describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group. A high level data model or the implementation data model can be used at this level.
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Sept. 2009
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This note was uploaded on 02/17/2010 for the course ACS ACS-3911 taught by Professor Chen during the Spring '10 term at Windsor.

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ExamMid09discussion - Analysis of Midterm-Examination 1(5 Describe the working process with a database system a database definition By the database

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