CSC 4402 20090826

CSC 4402 20090826 - CSC 4402 8/26/2009 Page 1 of 4...

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CSC 4402 8/26/2009 Page 1 of 4 Traditional model + dispersed control of data + redundancy exists + possible inconsistency Figure 1 – Traditional model Relational model + easier application development + reduced redundancy + less inconsistencies Figure 2 – Relational model
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CSC 4402 8/26/2009 Page 2 of 4 Integrity Data integrity means that all data is accurate and correct (i.e. has been checked to have correct values and meets all constraints) Integrity constraints are conditions that must be met by database values. Data abstraction One important purpose of DBMS is to provide its users with an abstract view of data, hiding the lower level details. The physical level + How is the data to be stored? The logical level + What data do we have? + What is the relationship among the data? Figure 3 – Simplified figure of database system
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CSC 4402 8/26/2009 Page 3 of 4 Figure 4 – ANSI/SPARC 3-level architecture Layers/levels of the database communicate via mappings/schemas which tell it how to format
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CSC 4402 20090826 - CSC 4402 8/26/2009 Page 1 of 4...

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