book

SQL and Relational Theory, 3rd Edition

by C.J. Date

November 2015

Intermediate to advanced

582 pages

16h 19m

English

O'Reilly Media, Inc.

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The relational model is much misunderstoodSome remarks on terminologyPrinciples not productsA review of the original modelModel vs. implementationProperties of relationsBase vs. derived relationsRelations vs. relvarsValues vs. variablesConcluding remarksExercisesAnswers

Types and relationsEquality comparisonsData value atomicityWhat’s a type?Scalar vs. nonscalar typesScalar types in SQLType checking and coercion in SQLCollations in SQLRow and table types in SQLConcluding remarksExercisesAnswers
What’s a tuple?Rows in SQLWhat’s a relation?Relations and their bodiesRelations are n-dimensionalRelational comparisonsTABLE_DUM and TABLE_DEETables in SQLColumn naming in SQLConcluding remarksExercisesAnswers
What’s wrong with duplicates?Duplicates: further issuesAvoiding duplicates in SQLWhat’s wrong with nulls?Avoiding nulls in SQLA remark on outer joinConcluding remarksExercisesAnswers
Updating is set levelRelational assignmentMore on candidate keysMore on foreign keysRelvars and predicatesRelations vs. typesExercisesAnswers
Some preliminariesMore on closureRestrictionProjectionJoinUnion, intersection, and differenceWhich operators are primitive?Formulating expressions one step at a timeWhat do relational expressions mean?Evaluating SQL table expressionsExpression transformationThe reliance on attribute namesExercisesAnswers
Exclusive unionSemijoin and semidifferenceExtendImage relationsDivideAggregate operatorsImage relations revisitedSummarizationSummarization revisitedGroup, ungroup, and relation valued attributes“What if” queriesA note on recursionWhat about ORDER BY?ExercisesAnswers
Type constraintsType constraints in SQLDatabase constraintsDatabase constraints in SQLTransactionsWhy database constraint checking must be immediateBut doesn’t some checking have to be deferred?Constraints and predicatesMiscellaneous issuesExercisesAnswers
Views are relvarsViews and predicatesRetrieval operationsViews and constraintsUpdate operationsWhat are views for?Views and snapshotsExercisesAnswers
Why do we need logic?Simple and compound propositionsSimple and compound predicatesQuantificationRelational calculusMore on quantificationSome equivalencesConcluding remarksExercisesAnswers
Some transformation lawsExample 1: Logical implicationExample 2: Universal quantificationExample 3: Implication and universal quantificationExample 4: Correlated subqueriesExample 5: Naming subexpressionsExample 6: More on naming subexpressionsExample 7: Dealing with ambiguityExample 8: Using COUNTExample 9: Another variationExample 10: UNIQUE quantificationExample 11: ALL or ANY comparisonsExample 12: GROUP BY and HAVINGExercisesAnswers
SELECT *Explicit tablesDot qualificationRange variablesSubqueries“Possibly nondeterministic” expressionsEmpty setsA simplified BNF grammarExercisesAnswers
The relational model vs. othersThe significance of theoryThe relational model definedDatabase variablesObjectives of the relational modelSome database principlesWhat remains to be done?
Vertical decompositionHorizontal decompositionWhat do the shaded entries mean?ConstraintsQueriesMore on predicatesExercisesAnswers
Functional segmentationShardingEventual consistencyThe Fernandez interview

Content preview from SQL and Relational Theory, 3rd Edition

SQL and Relational Theory

SQL is full of difficulties and traps for the unwary. You can avoid them if you understand relational theory, but only if you know how to put that theory into practice. In this book, Chris Date explains relational theory in depth, and demonstrates through numerous examples and exercises how you can apply it to your use of SQL.

This third edition has been revised, extended, and improved throughout. Topics whose treatment has been expanded include data types and domains, table comparisons, image relations, aggregate operators and summarization, view updating, and subqueries. A special feature of this edition is a new appendix on NoSQL and relational theory.

Could you write an SQL query to find employees who have worked at least once in every programming department in the company? And be sure it’s correct?
Why is proper column naming so important?
Nulls in the database cause wrong answers. Why? What you can do about it?
How can image relations help you formulate complex SQL queries?
SQL supports “quantified comparisons,” but they’re better avoided. Why? And how?

Database theory and practice have evolved considerably since Codd first defined the relational model, back in 1969. This book draws on decades of experience to present the most up to date treatment of the material available anywhere. Anyone with a modest to advanced background in SQL can benefit from the insights it contains. The book is product independent.

Chris Date has a stature that is unique ...