Data Modeling Essentials 2005 phần 10 ppt
Data Modeling Essentials 2005 phần 10 ppt
... some impact on data modeling. 16.2.1 Data Integration: Working with Existing Databases A data warehouse is not simply a collection of copies of records from source systems. It is a database that ... 16 Modeling for Data Warehouses and Data Marts Simsion-Witt_16 10/ 8/04 8:08 PM Page 488 Data warehouse design is particularly influenced by its role as a staging point between o...
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Data Modeling Essentials 2005 phần 1 ppsx
... format. 4 ■ Chapter 1 What Is Data Modeling? Figure 1.1 An information system. Report Program DATABASE Program data Report Program data data ProgramProgram data data 1 Data models can be presented ... 1 Chapter 10. Conceptual Data Modeling 273 10. 1 Designing Real Models 273 10. 2 Learning from Designers in Other Disciplines 275 10. 3 Starting the Modeling 276 10. 4 Pa...
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Data Modeling Essentials 2005 phần 2 potx
... involved if changes to the logical data model are contemplated. In developing a system, data modeling and process modeling usually proceed broadly in parallel. Data modeling principles remain important ... of data. In Chapter 7 we look at some extensions to the basic conventions and some alternative modeling languages. 1.15 Summary Data and databases are central to informati...
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Data Modeling Essentials 2005 phần 3 ppsx
... resulting database or system. This is a simplistic argument, and not likely to convince other stakeholders. 4 .10. 2 Modeling Only the Supertype One of the most common approaches to modeling the ... as well as being dependent on more than one owner entity. 102 ■ Chapter 3 The Entity-Relationship Approach Simsion-Witt_03 10/ 8/04 8:02 PM Page 102 However, if the business is an airline...
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Data Modeling Essentials 2005 phần 4 ppsx
... Identity Simsion-Witt_06 10/ 11/04 8:57 PM Page 184 datatype requires the number of digits after the decimal point to be spec- ified. If the decimal datatype is not available, the integer datatype must be ... currency datatype does not accommodate more than two digits after the decimal point, again the decimal datatype should be used. If the decimal datatype is not avail- able, the integer d...
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Data Modeling Essentials 2005 phần 5 pot
... Bulwer-Lytton 8.1 Data Modeling in the Real World In the preceding chapters, we have focused largely on learning the lan- guage of data modeling without giving much attention to the practicalities of modeling ... minimum list. 8.2.1 Recognition of Data Modeling Let us repeat what we said in Chapter 1: No database was ever built with- out a data model. Unfortunately, many datab...
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Data Modeling Essentials 2005 phần 6 pdf
... as those we use for selecting good 276 ■ Chapter 10 Conceptual Data Modeling Simsion-Witt _10 10/11/04 8:49 PM Page 276 Chapter 10 Conceptual Data Modeling “Our job is to give the client not what ... Relationships ■ 295 Figure 10. 17 Deliberate creation of asymmetry. Person associated with (lower ID) associated with (higher ID) Simsion-Witt _10 10/11/04 8:49 PM Page 295 300 ■ C...
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Data Modeling Essentials 2005 phần 7 potx
... “the price paid inclusive of tax” not “the prices paid 310 ■ Chapter 10 Conceptual Data Modeling Simsion-Witt _10 10/11/04 8:49 PM Page 310 This may sound complicated but, in practice, this iterative ... combina- tion of < ;Data Item 1 Name>, < ;Data Item 2 Name>, . . . and < ;Data Item n Name>.” 10. 18 The Assertions Approach ■ 317 Simsion-Witt _10 10/11/04 8:49...
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Data Modeling Essentials 2005 phần 8 pps
... include historical data in the same table as the corresponding current data, it is likely that different queries access current and historical data. Placing current and historical data in different ... improve the performance of queries on current data. You may prefer to include a copy of the current data in the historical data table to enable queries on all data to be written w...
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Data Modeling Essentials 2005 phần 9 ppsx
... 1968 15.1 The Problem Few areas of data modeling are the subject of as much confusion as the handling of time-related and time-dependent data. Perhaps we are modeling data for an insurance company. ... expect that the data to support this process rule is going to be held in the database. 14.2.3 What Rules Are Relevant to the Data Modeler? The data modeler should be concerned w...
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