Wiley SQL All In One Desk Reference For Dummies Jul 2007 ISBN 0470119284 pdf
by Allen G. Taylor
SQL
A L L - I N - O N E D E S K R E F E R E N C E
FOR
DUMmIES
‰
SQL
A L L - I N - O N E D E S K R E F E R E N C E
FOR
DUMmIES
‰
by Allen G. Taylor
SQL
A L L - I N - O N E D E S K R E F E R E N C E
FOR
DUMmIES
‰® SQL All-in-One Desk Reference For Dummies Published by Wiley Publishing, Inc.
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About the Author
Allen G. Taylor is a 30-year veteran of the computer industry and the author
of 25 books, including SQL For Dummies, Crystal Reports 10 For Dummies,
Database Development For Dummies, Access 2003 Power Programming with
VBA, and SQL Weekend Crash Course. He lectures internationally on data-
bases, networks, innovation, and entrepreneurship. He also teaches database development through a leading online education provider and teaches micro- processor design at Portland State University. For the latest news on Allen’s activities, check out www.DatabaseCentral.Info. You can contact Allen at allen.taylor@ieee.org.
Dedication
This book is dedicated to Joyce Carolyn Taylor, who still puts up with me after all these years.
Author’s Acknowledgments
First and foremost, I would like to acknowledge the help of Jim Melton, editor of the ISO/ANSI specification for SQL. Without his untiring efforts, this book, and indeed SQL itself as an international standard, would be of much less value. Andrew Eisenberg has also contributed to my knowledge of SQL through his writing. I would also like to thank my project editor, Nicole Sholly, and my acquisitions editor, Kyle Looper, for their key contributions to the production of this book. Thanks also to my agent, Carole McClendon of Waterside Productions, for her support of my career.
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Contents at a Glance
Introduction .................................................................1
Book I: SQL Concepts....................................................7
Chapter 1: Relational Database Basics ............................................................................9 Chapter 2: Modeling a System ........................................................................................27 Chapter 3: SQL Overview ................................................................................................49 Chapter 4: SQL and the Relational Model .....................................................................59 Chapter 5: The Major Components of SQL ...................................................................67 Chapter 6: SQL Characteristics ......................................................................................89 Book II: Relational Database Development .................117 Chapter 1: System Development Overview ................................................................119 Chapter 2: Building a Database Model.........................................................................135 Chapter 3: Balancing Performance and Correctness.................................................159 Chapter 4: Creating a Database with SQL....................................................................189 Book III: SQL Queries................................................201 Chapter 1: Values, Variables, Functions, and Expressions........................................203 Chapter 2: SELECT Statements and Modifying Clauses ............................................227 Chapter 3: Querying Multiple Tables with Subqueries..............................................269 Chapter 4: Querying Multiple Tables with Relational Operators.............................297 Chapter 5: Cursors .........................................................................................................315 Book IV: Data Security..............................................325 Chapter 1: Protecting Against Hardware Failure and External Threats ..................327 Chapter 2: Protecting Against User Errors and Conflicts..........................................343 Chapter 3: Assigning Access Privileges .......................................................................371 Chapter 4: Error Handling .............................................................................................383 Book V: SQL and Programming ..................................397 Chapter 1: Database Development Environments .....................................................399 Chapter 2: Interfacing SQL to a Procedural Language...............................................403 Chapter 3: Using SQL in an Application Program.......................................................409 Chapter 4: Designing a Sample Application ................................................................423 Chapter 5: Building a Sample Application...................................................................443 Chapter 6: SQL’s Procedural Capabilities....................................................................459
Book VI: SQL and XML..............................................489
Chapter 1: XML/SQL Basics...........................................................................................491 Chapter 2: Storing XML Data in SQL Tables................................................................515 Chapter 3: Retrieving Data from XML Documents .....................................................535 Book VII: Database Tuning Overview..........................551 Chapter 1: Tuning the Database ...................................................................................553 Chapter 2: Tuning the Environment.............................................................................565 Chapter 3: Finding and Eliminating Bottlenecks ........................................................587 Book VIII: Appendixes...............................................619 Appendix A: SQL:2003 Reserved Words ......................................................................621 Appendix B: Glossary ....................................................................................................629
Index .......................................................................639
Table of Contents
Introduction..................................................................1
About This Book...............................................................................................1 Foolish Assumptions .......................................................................................2 Conventions Used in This Book .....................................................................2 What You Don’t Have to Read ........................................................................3 How This Book Is Organized...........................................................................3
Book I: SQL Concepts.............................................................................3 Book II: Relational Database Development .........................................3 Book III: SQL Queries .............................................................................4 Book IV: Data Security ...........................................................................4 Book V: SQL and Programming.............................................................4 Book VI: SQL and XML ...........................................................................4 Book VII: Database Tuning Overview...................................................5 Book VIII: Appendixes............................................................................5
Icons Used in This Book..................................................................................5 Where to Go from Here....................................................................................6
Book I: SQL Concepts ....................................................7
Chapter 1: Relational Database Basics . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Data Files and Databases ................................................................................9 Irreducible complexity.........................................................................10 The complex program/simple data organization ...................10 The simple program/complex data organization ...................12 Which type of organization is better?................................................12 Databases, Queries, and Database Applications .......................................13 Making data useful ...............................................................................14 Retrieving the data you want — and only the data you want ........14 Competing Database Models ........................................................................14 The hierarchical database model.......................................................15 The network database model .............................................................17 The relational database model ...........................................................20 What makes a database relational? ..........................................20 Codd’s Rules................................................................................20 Inherent flexibility ......................................................................23 The object-oriented database.............................................................23 The object-relational database ...........................................................23
SQL All-in-One Desk Reference For Dummies xiv
Chapter 2: Modeling a System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Capturing the Users’ Data Model .................................................................27 Identifying and interviewing stakeholders........................................27 Reconciling conflicting requirements ................................................28 Obtaining stakeholder buy-in .............................................................29 Translating the Users’ Data Model to a Relational Model ........................29 Entity-Relationship modeling techniques .........................................29 Entities .........................................................................................30 Attributes.....................................................................................30 Identifiers.....................................................................................31 Relationships...............................................................................31 Drawing Entity-Relationship diagrams ..............................................34 Maximum cardinality .................................................................34 Minimum cardinality ..................................................................35 Advanced E-R model concepts ...........................................................37 Strong entities and weak entities..............................................37 ID-dependent entities .................................................................39 Supertype and subtype entities................................................39 Incorporating business rules ....................................................40 A simple example of an E-R model .....................................................41 A slightly more complex example ......................................................42 Problems with complex relationships ...............................................46 Simplifying relationships using normalization .................................47 Translating an E-R model into a relational model ............................47 The Relational Database Hierarchy .............................................................47 Chapter 3: SQL Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 Where SQL Came From..................................................................................49 What SQL Does ...............................................................................................50 The ANSI/ISO SQL Standard..........................................................................51 What SQL Does Not Do..................................................................................51 Available Implementations ...........................................................................52 Microsoft Access ..................................................................................52 Microsoft SQL Server ...........................................................................56 IBM DB2 .................................................................................................56 Oracle.....................................................................................................56 InterBase................................................................................................57 MySQL....................................................................................................57 PostgreSQL ............................................................................................57 Chapter 4: SQL and the Relational Model . . . . . . . . . . . . . . . . . . . . . . . .59 Sets, Relations, Multisets, and Tables .........................................................59 Functional Dependencies..............................................................................60
Table of Contents xv
Users ................................................................................................................63 Privileges.........................................................................................................63 Schemas ..........................................................................................................64 Catalogs ...........................................................................................................64 Connections, Sessions, and Transactions...................................................64 Routines ..........................................................................................................65 Paths ................................................................................................................66
Chapter 5: The Major Components of SQL . . . . . . . . . . . . . . . . . . . . . . .67
The Data Definition Language (DDL) ...........................................................67 The containment hierarchy ................................................................67 Creating tables ......................................................................................68 Specifying columns ..............................................................................68 Specifying constraints ........................................................................69 Column constraints ....................................................................70 Table constraints ........................................................................71 Assertions....................................................................................71 Creating other objects .........................................................................72 Views ............................................................................................72 Schemas .......................................................................................77 Domains .......................................................................................77 Modifying tables and other objects ...................................................78 Removing tables and other objects ...................................................78 The Data Manipulation Language (DML) ....................................................78 Retrieving data from a database.........................................................79 Adding data to a table..........................................................................80 Adding data the dull and boring way (typing it in) ................80 Adding incomplete data.............................................................81 Adding data in the fastest and most efficient way: Bypassing typing altogether..................................................81 Updating data in a table ......................................................................81 Deleting data from a table ...................................................................84 Updating views .....................................................................................85 The Data Control Language (DCL) ...............................................................86 Granting access privileges ..................................................................86 Revoking access privileges .................................................................87 Preserving database integrity with transactions ............................87Chapter 6: SQL Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
Executing SQL Statements ............................................................................89 Interactive SQL .....................................................................................90 Challenges to combining SQL with a host language ........................90 Embedded SQL .....................................................................................91 Module language ..................................................................................93SQL All-in-One Desk Reference For Dummies xvi
SQL’s Data Types ............................................................................................94 Exact numerics .....................................................................................95
INTEGER.......................................................................................95 SMALLINT ....................................................................................96 BIGINT ..........................................................................................96 NUMERIC......................................................................................96 DECIMAL ......................................................................................96 BINARY LARGE OBJECT (BLOB)...............................................97
Approximate numerics ........................................................................97 REAL .............................................................................................97 DOUBLE PRECISION ...................................................................98 FLOAT...........................................................................................98
Character strings..................................................................................99 CHARACTER ................................................................................99 CHARACTER VARYING ...............................................................99 CHARACTER LARGE OBJECT (CLOB) ......................................99 NATIONAL CHARACTER, NATIONAL CHARACTER
VARYING, and NATIONAL CHARACTER LARGE OBJECT......................................................................100
Booleans ..............................................................................................101 Datetimes.............................................................................................101
DATE ...........................................................................................101 TIME WITHOUT TIME ZONE....................................................101 TIME WITH TIME ZONE............................................................102 TIMESTAMP WITHOUT TIME ZONE .......................................102 TIMESTAMP WITH TIME ZONE ...............................................102 Intervals...............................................................................................103
XML type .............................................................................................103 Row types ............................................................................................104 Collection types..................................................................................105
ARRAY ........................................................................................105 Multiset ......................................................................................105
REF types .............................................................................................106 User-defined types .............................................................................106
Distinct types ............................................................................106 Structured types .......................................................................107
Data type summary ............................................................................109 Handling Null Values ....................................................................................110 Applying Constraints ...................................................................................111
Column constraints............................................................................111 NOT NULL..................................................................................111 UNIQUE ......................................................................................112 CHECK ........................................................................................112
Table constraints................................................................................113
Table of Contents xvii
Book II: Relational Database Development ..................117
Chapter 1: System Development Overview . . . . . . . . . . . . . . . . . . . . . .119 The Components of a Database System....................................................119 The database.......................................................................................120 The database engine ..........................................................................120 The DBMS front end ...........................................................................120 The database application..................................................................120 The user...............................................................................................121 The System Development Life Cycle .........................................................121 Definition phase..................................................................................122 Requirements phase ..........................................................................123 Establishing requirements: An example ................................123 The users’ data model..............................................................124 Statement of Requirements .....................................................124 Evaluation phase ................................................................................125 Determining project scope ......................................................126 Reassessing feasibility .............................................................127 Documenting the evaluation phase........................................127 Design phase .......................................................................................127 Designing the database............................................................128 The database application ........................................................129 Documenting the design phase...............................................129 Implementation phase .......................................................................130 Final documentation and testing phase ..........................................130 Testing the system with sample data.....................................131 Finalizing the documentation..................................................132 Delivering the results (and celebrating)................................132 Maintenance phase ............................................................................132 Chapter 2: Building a Database Model . . . . . . . . . . . . . . . . . . . . . . . . .135 Finding and Listening to Interested Parties..............................................135 Your immediate supervisor...............................................................136 The users.............................................................................................136 The standards organization ..............................................................137 Upper management............................................................................137 Building Consensus......................................................................................138 What do people want, and how badly do they want it? ................138 Arriving at a consensus .....................................................................139 The three-option proposal ................................................................139 The Entity-Relationship Modeling Method ...............................................140 Entities .................................................................................................140 Attributes ............................................................................................141
SQL All-in-One Desk Reference For Dummies xviii
Maximum cardinality .........................................................................145 Minimum cardinality ..........................................................................145 Business rules.....................................................................................147
Building a Relational Model ........................................................................147 Different worlds, different terminology ...........................................147 The relational tradition......................................................................147 What exactly is a relation? ................................................................149 Functional dependencies ..................................................................149 Keys......................................................................................................150
Being Aware of the Danger of Anomalies ..................................................150 Eliminating anomalies........................................................................152 The higher normal forms ..................................................................155
The Database Integrity versus Performance Tradeoff ............................156
Chapter 3: Balancing Performance and Correctness . . . . . . . . . . . . .159 Designing a Sample Database .....................................................................160 The E-R model for Honest Abe’s ......................................................160 Converting an E-R model into a relational model ..........................161 Normalizing a relational model.........................................................162 Handling binary relationships ..........................................................164 A sample conversion..........................................................................168 Maintaining Integrity ...................................................................................170 Entity integrity ....................................................................................171 Domain integrity.................................................................................172 Referential integrity ...........................................................................172 Avoiding Data Corruption ...........................................................................174 Speeding Data Retrievals ............................................................................175 Hierarchical storage...........................................................................176 Full table scans ...................................................................................177 How indexes work ..............................................................................177 Creating the right indexes .................................................................177 Indexes and the ANSI/ISO Standard...........................................................178 Index costs ..........................................................................................178 Query type dictates the best index..................................................178 Point query................................................................................178 Multipoint query.......................................................................179 Range query ..............................................................................179 Prefix match query ...................................................................179 Extremal query..........................................................................179 Ordering query..........................................................................180 Grouping query.........................................................................180 Equi-join query..........................................................................180 Data structures used for indexes .....................................................180 B+ trees ......................................................................................181
Table of Contents xix
Index effect on join performance .....................................................183 Table size as an indexing consideration..........................................183 Indexes versus full-table scans.........................................................183
Reading SQL Server Execution Plans.........................................................183 Robust execution plans .....................................................................183 A sample database .............................................................................184
A typical query..........................................................................185 The execution plan ...................................................................185 Running the Database Engine Tuning Advisor......................185
Hot Tables and Load Balancing..................................................................187
Chapter 4: Creating a Database with SQL . . . . . . . . . . . . . . . . . . . . . . .189 First Things First: Planning Your Database...............................................189 Building Tables .............................................................................................190 Locating table rows with keys ..........................................................191 Using the CREATE TABLE statement................................................192 Setting Constraints.......................................................................................193 Column constraints............................................................................193 Table constraints................................................................................194 Keys and Indexes .........................................................................................194 Ensuring Data Validity with Domains ........................................................194 Establishing Relationships between Tables .............................................195 Altering Table Structure ..............................................................................198 Deleting Tables .............................................................................................199
Book III: SQL Queries ................................................201
Chapter 1: Values, Variables, Functions, and Expressions . . . . . . . .203 Entering Data Values....................................................................................203 Row values have multiple parts .......................................................203 Identifying values in a column ..........................................................204 Literal values don’t change ...............................................................204 Variables Vary ...............................................................................................205 Special Variables Hold Specific Values ......................................................206 Working with Functions...............................................................................207 Summarizing data with set functions ..............................................207 COUNT .......................................................................................207 AVG .............................................................................................208 MAX ............................................................................................208 MIN .............................................................................................209 SUM.............................................................................................209 Dissecting data with value functions ...............................................209SQL All-in-One Desk Reference For Dummies xx
Using Expressions ........................................................................................217 Numeric value expressions ...............................................................217 String value expressions....................................................................218 Datetime value expressions ..............................................................218 Interval value expressions ................................................................219 Boolean value expressions................................................................219 Array value expressions ....................................................................220 Conditional value expressions..........................................................220
Handling different cases ..........................................................221 The NULLIF special CASE ........................................................222 Bypassing null values with COALESCE ..................................223
Converting data types with a CAST expression .............................223 Casting one SQL data type to another ...................................224 Using CAST to overcome data type incompatibilities between SQL and its host language....................................224
Row value expressions ......................................................................225
Chapter 2: SELECT Statements and Modifying Clauses . . . . . . . . . . .227 Finding Needles in Haystacks with the SELECT Statement ....................227 Modifying Clauses ........................................................................................228 FROM clauses......................................................................................228 WHERE clauses ...................................................................................229 Comparison predicates............................................................230 BETWEEN...................................................................................231 IN and NOT IN ...........................................................................232 LIKE and NOT LIKE ...................................................................234 SIMILAR......................................................................................235 NULL...........................................................................................235 ALL, SOME, ANY .......................................................................236 EXISTS ........................................................................................239 UNIQUE ......................................................................................240 DISTINCT....................................................................................240 OVERLAPS .................................................................................241 MATCH .......................................................................................241 The MATCH predicate and referential integrity....................243 Logical connectives............................................................................245 AND.............................................................................................245 OR ...............................................................................................246 NOT ............................................................................................247 GROUP BY clauses .............................................................................247 HAVING clauses ..................................................................................249 ORDER BY clauses..............................................................................249 Tuning Queries .............................................................................................251 SELECT DISTINCT...............................................................................252
Table of Contents xxi
Chapter 3: Querying Multiple Tables with Subqueries . . . . . . . . . . .269
What Is a Subquery? ....................................................................................269 What Subqueries Do ....................................................................................269 Subqueries that return multiple values...........................................270 Subqueries that retrieve rows satisfying a condition ..........270 Subqueries that retrieve rows thatdon’t satisfy a condition.......................................................271 Subqueries that return a single value..............................................272 Quantified subqueries return a single value...................................275 Correlated subqueries .......................................................................277
Using a subquery as an existence test...................................278 Introducing a correlated subquery with the IN keyword ....279 Introducing a correlated subquery with a comparison operator................................................279 Correlated subqueries in a HAVING clause ...........................281
Using Subqueries in INSERT, DELETE, and UPDATE Statements ...........282 Tuning Considerations for Statements Containing Nested Queries ......285 Tuning Correlated Subqueries....................................................................290
Chapter 4: Querying Multiple Tables with Relational Operators . . .297
UNION ............................................................................................................297 UNION ALL ..........................................................................................299 UNION CORRESPONDING ..................................................................300 INTERSECT....................................................................................................300 EXCEPT..........................................................................................................302 JOINS..............................................................................................................303 Cartesian product or cross join........................................................303 Equi-join...............................................................................................305 Natural join..........................................................................................307 Condition join .....................................................................................307 Column-name join ..............................................................................308 Inner join .............................................................................................309 Outer join ............................................................................................310 Left outer join............................................................................310 Right outer join .........................................................................312 Full outer join ............................................................................313 ON versus WHERE........................................................................................313 Join Conditions and Clustering Indexes....................................................314Chapter 5: Cursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .315