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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... 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 information systems. Every database ... 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...

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... Approach ■ 3 15 Simsion-Witt_10 10/11/04 8:49 PM Page 3 15 10. 15 Comparison with the Process Model One of the best means of verifying a data model is to ensure that it includes all the necessary data to ... 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 to...

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... Many-to-Many Relationships 450 14.7 Summary 450 Chapter 15 Time-Dependent Data 451 15. 1 The Problem 451 15. 2 When Do We Add the Time Dimension? 452 15. 3 Audit Trails and Snapshots 452 15. 3.1 The Basic Audit ... Basic Audit Trail Approach 453 15. 3.2 Handling Nonnumeric Data 458 15. 3.3 The Basic Snapshot Approach 458 15. 4 Sequences and Versions 462 15. 5 Handling De...

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... 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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... (true/false) 152 ■ Chapter 5 Attributes and Columns Simsion-Witt_ 05 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 ... currency unit. 156 ■ Chapter 5 Attributes and Columns 5 Date, C.J. Relational Database Writings 1989-1991, Pearson Education POD, 1992, Ch. 12. Simsion-Witt_ 05...

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... Unfortunately, much that is written and taught about data modeling makes this very naive assumption. Experienced data modelers do not try to solicit a data model directly, but take a holistic approach. ... 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 cli...

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... No 50 227 B Malik 1234 23 45 37289 J Smith 1234 Assignment Date 27/2/ 95 2/3/ 95 28/2/ 95 Figure 12 .5 Alternative implementations of relationships in an SQL99 DBMS. Simsion-Witt_12 10/11/04 8 :58 PM ... 3999 Victoria 4000 4999 Queensland 50 00 59 99 South Australia etc. Figure 13.16 Data derivable across rows. Simsion-Witt_13 10/11/04 9 :54 PM Page 410 exist in a 5NF structure. In...

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... Date 18 12/21/93 Maintenance 1 12/ 25/ 93 63 12/23/93 Local Holiday 2 12/ 25/ 93 3 12/ 25/ 93 National Closure 4 12/ 25/ 93 Date Reason 5 12/ 25/ 93 12/ 25/ 93 Christmas 6 12/ 25/ 93 Figure 14.12 Post office closuresnormalized ... Reason 18 12/21/93 Maintenance 1 12/ 25/ 93 Christmas 63 12/23/93 Local Holiday 2 12/ 25/ 93 Christmas 3 12/ 25/ 93 Christmas 4 12/ 25/ 93 Christmas 5 12/ 25/...

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... 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 ... the data management function. 50 2 ■ Chapter 17 Enterprise Data Models and Data Management 3 The International Data Managers Association (DAMA) at www.dama.org is a worldwide bod...

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