View Updating and Relational Theory

Solving the View Update Problem

C. J. Date (Autor)

Buch | Softcover

260 Seiten

2013
O'Reilly Media, Inc, USA (Verlag)
9781449357849 (ISBN)

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Views are a key part of database technology, but they're often considered read-only. In this book, Chris Date - a leading expert in relational databases - offers practical techniques that allow you to update the views that a database presents to you.

Views are virtual tables. That means they should be updatable, just as "real" or base tables are. In fact, view updatability isn't just desirable, it's crucial, for practical reasons as well as theoretical ones. But view updating has always been a controversial topic. Ever since the relational model first appeared, there has been widespread skepticism as to whether (in general) view updating is even possible. In stark contrast to this conventional wisdom, this book shows how views, just like base tables, can always be updated (so long as the updates don't violate any integrity constraints). More generally, it shows how updating always ought to work, regardless of whether the target is a base table or a view. The proposed scheme is 100% consistent with the relational model, but rather different from the way updating works in SQL products today.
This book can:

Help database products improve in the future
Help with a "roll your own" implementation, absent such product improvements
Make you aware of the crucial role of predicates and constraints
Show you how relational products are really supposed to behave
Anyone with a professional interest in the relational model, relational technology, or database systems in general can benefit from this book.

C.J. Date has a stature that is unique within the database industry. C.J. is a prolific writer, and is well-known for his best-selling textbook: An Introduction to Database Systems (Addison Wesley). C.J. is an exceptionally clear-thinking writer who can lay out principles and theory in a way easily understood by his audience.

Chapter 1 A Motivating Example
The Principle of Interchangeability
Base Tables Only: Constraints
Base Tables Only: Compensatory Actions
Views: Constraints and Compensatory Actions
There’s No Magic
Concluding Remarks
Chapter 2 The Technical Context
Relations and Relvars
Relational Assignment
Integrity Constraints
Relvar Predicates
Matching, not Matching, and Extend
Databases and Dbvars
Chapter 3 The View Concept: A Closer Look
The View Update Problem
Views are Pseudovariables
Data Independence
How Not to do it
Constraints and Predicates
Information Equivalence
Concluding Remarks
Chapter 4 Restriction Views
The Motivating Example Revisited
More on Compensatory Actions
What About Triggers?
What About Explicit Update Operations?
Suppliers and Shipments
The Motivating Example Continued
Putting it All Together
The Point at Last
Overlapping Restrictions
Concluding Remarks
Chapter 5 Projection Views
Example 1: A Nonloss Decomposition
Example 1 Continued: The Projection Relvars
Example 1 Continued: Views
Example 2: Another Nonloss Decomposition
Example 3: A Lossy Decomposition
Concluding Remarks
Chapter 6 Join Views I: One to One Joins
Example 1: Information Equivalence
Example 2: Information Hiding
Concluding Remarks
Chapter 7 Join Views II: Many to Many Joins
Example 1: Information Equivalence
Projection Views Revisited
Example 2: Information Hiding
Concluding Remarks
Chapter 8 Join Views III: One to Many Joins
Example 1: Information Equivalence
Example 2: Information Hiding
Concluding Remarks
Chapter 9 Intersection Views
Example 1: Explicit Overlap
Example 2: Implicit Overlap
Concluding Remarks
Chapter 10 Union Views
Example 1: Disjoint Union
Example 2: Explicit Overlap
Example 3: Implicit Overlap
Concluding Remarks
Chapter 11 Difference Views
Example 1: Implicit Overlap
Example 2: Explicit Overlap
Concluding Remarks
Chapter 12 Group and Ungroup Views
The Group and Ungroup Operators
A Group / Ungroup Example
A Summarize Example
Chapter 13 Extension and Summarization Views
An Extend Example
Another Summarize Example
Chapter 14 Updating through Expressions
Semantics not Syntax (?)
Some well known Tautologies
“Semantic Transformations”
Information Equivalence Revisited
Concluding Remarks
Chapter 15 Ambiguity Revisited
Predicates and Constraints Revisited
An Intersection Example
Union and Difference Examples
More on Predicates
Concluding Remarks
Appendix Some Remarks on Relational Assignment
Appendix Relational Operators

Reihe/Serie	Theory in Practice
Verlagsort	Sebastopol
Sprache	englisch
Maße	178 x 233 mm
Gewicht	422 g
Themenwelt	Mathematik / Informatik ► Informatik ► Datenbanken
Schlagworte	data independence, SQL, Relational databases, views, • Relational databases, SQL, data independence, views, • Relationale Datenbank • views, SQL, Relational databases, data independence,
ISBN-13	9781449357849 / 9781449357849
Zustand	Neuware