Data Modeling Essentials 2005 phần 7 potx
Data Modeling Essentials 2005 phần 7 potx
... combina- tion of < ;Data Item 1 Name>, < ;Data Item 2 Name>, . . . and < ;Data Item n Name>.” 10.18 The Assertions Approach ■ 3 17 Simsion-Witt_10 10/11/04 8:49 PM Page 3 17 10.18.2.3. Attribute ... accepting a data model. 10.16 Testing the Model with Sample Data If sample data is available, there are few better ways of communicating and verifying a data model than...
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Data Modeling Essentials 2005 phần 2 potx
... HO Employee Number Qualification Description Qualification Year 012 67 Bachelor of Arts 1 970 012 67 Master of Arts 1 973 012 67 Doctor of Philosophy 1 976 70 964 Bachelor of Arts 1969 226 17 Bachelor of Arts 1 972 226 17 Master of Arts 1 977 Employee Table ... Philosophy 1 976 70 964 Bachelor of Arts 1969 226 17 Bachelor of Arts 1 972 226 17 Master of Arts 1 977 Employee Numbe...
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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 ... Concept 219 7. 3.6 Chen Conventions in Practice 220 7. 4 Using UML Object Class Diagrams 220 7. 4.1 A Conceptual Data Model in UML 221 7. 4.2 Advantages of UML 222 7. 5 Object...
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Data Modeling Essentials 2005 phần 3 ppsx
... data. You obviously need to be careful in choosing not to reflect real-world overlap in the data model. Failure to recognize overlaps among parties is one of the most common faults in older database ... but whether the database structure, as specified by the data model, is the best place for them. Recall that one of the reasons we give so much attention to designing a sound data model...
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Data Modeling Essentials 2005 phần 4 ppsx
... 10/8/04 7: 56 PM Page 152 5.4.4 Column Datatype and Length Requirements We now look at the translation of attribute types into column datatypes. If your DBMS does not support UDTs (user-defined datatypes), ... varchar datatype 7 (depending on the particular properties of these datatypes in the DBMS being used), unless it is known that nonnumeric values will never be required, in which case...
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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
... same 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 ... needs, as well as detailed data requirements. Sources of requirements and ideas include 270 ■ Chapter 9 The Business Requirements Simsion-Witt_09 10/8/04 7: 47 PM Page 270 sugges...
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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. ... attribute is optional (nullable) (a data validation rule) 7. The DBMS datatype of each attribute (e.g., if the attribute is given a numeric datatype, this specifies a data valida...
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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 ... consistent results. 478 ■ Chapter 16 Modeling for Data Warehouses and Data Marts Simsion-Witt_16 10/8/04 8:08 PM Page 478 Chapter 17 Enterprise Data Models and Data Manageme...
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