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自E.F Codd于1969年首次定义关系模式以来,数据库理论与实践就一直在发展。本书独立于任何SQL,产品,描绘了关系数据库理论十几年来的研究进展,为读者介绍了有关关系数据库理论的最新知识。任何具有一定SQL知识的人都可以从中的很多方面受益。C.J. Date于1970的早期在IBM开始从事数据库方面工作。他是一个多产的作者,其著名的教材是“An Introduction to Database Systems(Addison-Wesley)”,该书被广泛地认为是关于数据库管理基础知识的最好教科书之一。数据库是否应该使用视图而不是基表来访问?数据库中的Null是否使你得到了错误的答案,为什么?关于Null,你又可以做些什么呢?是否可以编写一个SQL查询,通过这个查询,可以得到在同一个部门中同时工作超过六个月的员工?SQL支持“量化的比较”,但是最好避免使用它们。为什么?你又该如何来避免使用它们?约束是非常重要的,但是大部分的SQL一产品都没有恰当地支持它们。为了解决这个问题,你能做些什么呢?


Understanding SQL's underlying theory is the best way to guarantee that your SQL code is correct and your database schema is robust and maintainable. On the other hand, if you're not well versed in the theory, you can fall into several traps. In SQL and Relational Theory, author C.J. Date demonstrates how you can apply relational theory directly to your use of SQL. With numerous examples and clear explanations of the reasoning behind them, you'll learn how to deal with common SQL dilemmas, such as: 

Should database access granted be through views instead of base tables? 

Nulls in your database are causing you to get wrong answers. Why? What can you do about it? 

Could you write an SQL query to find employees who have never been in the same department for more than six months at a time? 

SQL supports "quantified comparisons," but they're better avoided. Why? How do you avoid them? 

Constraints are crucially important, but most SQL products don't support them properly. What can you do to resolve this situation? 

Database theory and practice have evolved since Edgar Codd originally defined the relational model back in 1969. Independent of any SQL products, SQL and Relational Theory draws on decades of research to present the most up-to-date treatment of the material available anywhere. Anyone with a modest to advanced background in SQL will benefit from the many insights in this book.


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Chapter 1 Setting the Scene
The Relational Model Is Much Misunderstood
Some Remarks on Terminology
Principles, Not Products
A Review of the Original Model
Model vs. Implementation
Properties of Relations
Base vs. Derived Relations
Relations vs. Relvars
Values vs. Variables
Concluding Remarks
Chapter 2 Types and Domains
Types and Relations
Equality Comparisons
Data Value Atomicity
What's a Type?
Scalar vs. Nonscalar Types
Scalar Types in SQL
Type Checking and Coercion in SQL
Collations in SQL
Row and Table Types in SQL
Concluding Remarks
Chapter 3 Tuples and Relations, Rows and Tables
What's a Tuple?
Rows in SQL
What's a Relation?
Relations and Their Bodies
Relations Are n-Dimensional
Relational Comparisons
Tables in SQL
Column Naming in SQL
Concluding Remarks
Chapter 4 No Duplicates, No Nulls
What's Wrong with Duplicates?
Duplicates: Further Issues
Avoiding Duplicates in SQL
What's Wrong with Nulls?
Avoiding Nulls in SQL
A Remark on Outer Join
Concluding Remarks
Chapter 5 Base Relvars, Base Tables
Data Definitions
Updating Is Set Level
Relational Assignment
More on Candidate Keys
More on Foreign Keys
Relvars and Predicates
Relations vs. Types
Chapter 6 SQL and Relational Algebra I: The Original Operators
Some Preliminaries
More on Closure
Union, Intersection, and Difference
Which Operators Are Primitive?
Formulating Expressions a Step at a Time
What Do Relational Expressions Mean?
Evaluating SQL Table Expressions
Expression Transformation
The Reliance on Attribute Names
Chapter 7 SQL and Relational Algebra II: Additional Operators
Semijoin and Semidifference
Image Relations
Aggregate Operators
Image Relations bis
Summarization bis
Group and Ungroup
"What If" Queries
What About ORDER BY?
Chapter 8 SQL and Constraints
Type Constraints
Type Constraints in SQL
Database Constraints
Database Constraints in SQL
Why Database Constraint Checking Must Be Immediate
But Doesn't Some Checking Have to Be Deferred?
Constraints and Predicates
Miscellaneous Issues
Chapter 9 SQL and Views
Views Are Relvars
Views and Predicates
Retrieval Operations
Views and Constraints
Update Operations
What Are Views For?
Views and Snapshots
Chapter 10 SQL and Logic
Simple and Compound Propositions
Simple and Compound Predicates
Relational Calculus
More on Quantification
Some Equivalences
Concluding Remarks
Chapter 11 Using Logic to Formulate SQL Expressions
Some Transformation Laws
Example 1: Logical Implication
Example 2: Universal Quantification
Example 3: Implication and Universal Quantification
Example 4: Correlated Subqueries
Example 5: Naming Subexpressions
Example 6: More on Naming Subexpressions
Example 7: Dealing with Ambiguity
Example 8: Using COUNT
Example 9: Join Queries
Example 10: UNIQUE Quantification
Example 11: ALL or ANY Comparisons
Example 12: GROUP BY and HAVING
Chapter 12 Miscellaneous SQL Topics
Explicit Tables
Name Qualification
Range Variables
"Possibly Nondeterministic" Expressions
Empty Sets
A BNF Grammar for SQL Table Expressions
Appendix The Relational Model
The Relational Model vs. Others
The Relational Model Defined
Objectives of the Relational Model
Some Database Principles
What Remains to Be Done?
Appendix Database Design Theory
The Place of Design Theory
Functional Dependencies and Boyce/Codd Normal Form
Join Dependencies and Fifth Normal Form
Two Cheers for Normalization
Some Remarks on Physical Design
Concluding Remarks
Appendix Answers to Exercises
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Appendix Suggestions for Further Reading

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