Wrox SQL Functions Programmers Reference Apr 2005 ISBN 0764569015 pdf

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Arie Jones

Ryan K. Stephens

Ronald R. Plew

Robert F. Garrett

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Published by Wiley Publishing, Inc. 10475 Crosspoint Boulevard Indianapolis, IN 46256 www.wiley.com

ISBN 13 978-0-7645-6901-2 ISBN 10 0-7645-6901-5

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Library of Congress Cataloging-in-Publication Data:

SQL functions programmer’s reference / Arie Jones ... [et al.]. p. cm.

Includes bibliographical references and index. ISBN 0-7645-6901-5 (paper/website : alk. paper) 1. SQL (Computer program language) I. Jones, Arie.

QA76.73.S67S674 2005 005.13’3--dc22

2005002765

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Arie Jones

Arie Jones is a senior database administrator for Perpetual Technologies, Inc. (www.perptech.com). He holds a master’s degree in physics from Indiana State University and also works as the chief Web architect/DBA for the USPFO for Indiana. Arie’s main specialty is in developing .NET-based database solutions for the gov-ernment. He and his wife and family live outside of Indianapolis, Indiana.

Ryan K. Stephens

Ryan Stephens is the president and CEO of Perpetual Technologies, Inc. (www.perptech.com), an Indianapolis-based IT firm specializing in database technologies. Ryan has been working with SQL and databases for 15 years and has held the positions of project manager, database administrator, and programmer/analyst. Ryan has been teaching database courses for local universities since 1997 and has authored several internationally published books on topics such as database design, SQL, database architecture, database administration, and Oracle. Ryan enjoys discovering new ways to optimize the use of technology to streamline business operations, as well as empowering others to do the same. Ryan and his wife live in Indianapolis with their three children.

Ronald R. Plew

Ronald R. Plew is vice president and CIO for Perpetual Technologies, Inc. (www.perptech.com) in Indianapolis, Indiana. Ron is a Certified Oracle Professional. He has coauthored several internationally published books on SQL and database technology. Ron is also an adjunct professor for Vincennes University in Indiana, where he teaches SQL and various database courses. Ron holds a bachelor of science degree in business administration/management from Indiana Institute of Technology out of Fort Wayne, Indiana. Ron recently retired from the Indiana Army National Guard, where he served as a programmer/analyst. His hobbies include automobile racing, chess, golf, and collecting Indy 500 memorabilia. Ron resides in Indianapolis with his wife Linda.

Robert F. Garrett

Bob Garrett is the software development manager at Perpetual Technologies, Inc. (www.perptech.com). Bob’s languages of preference are Java, C++, and English. He has extensive experience integrating appli-cations with relational databases. Bob has a degree in computer science and mathematics from Purdue University, and lives with his wife and daughter near Indianapolis.

Alex Kriegel

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Joshua Stephens

Joshua Stephens is a systems administrator/DBA for Perpetual Technologies, Inc. (www.perptech.com). He has eight years of experience in various IT areas. As a former technical writer and trainer, he contin-ues to enjoy helping others through writing. He holds a bachelor of arts degree in pure mathematics and physics from Franklin College. He lives in Franklin, Indiana, with his wife and daughter.

Richard Bulley

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Acquisitions Editor

Jim Minatel

Development Editor

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— Arie Jones

For Tina, Daniel, Autumn, and Alivia. You are my inspiration.

— Ryan Stephens

For Linda

— Ron Plew

For Becky and Libby

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Acknowledgments

Shortly after we accepted this project, it became clear how much of a team effort would be needed to make this book a must-have for anyone’s SQL library. Fortunately, I have an incredible technical team that knows how to come together and get the job done. Most of my thanks go to Arie Jones. Arie stepped up when I needed the most help, unafraid of commitment, confidently accepting another aggressive assignment. Our author team included Arie Jones, Ron Plew, Bob Garrett, Alex Kriegel, and myself. Contributing authors were Joshua Stephens and Richard Bulley. I cannot say enough about their profes-sionalism and technical proficiency. Thank you for being part of another successful project!

Probably as no surprise to the Wiley audience, the author team thanks the editorial staff at Wiley, which is one of the best with whom we have had the pleasure of working. Specifically, we appreciate Jim Minatel’s efforts and confidence in our team, Kevin Shafer’s strict attention to detail, and the technical editorial team’s thoroughness. Their dedication, patience, and thoroughness, we believe, reflect directly on the quality and timely delivery of this book, which would not have been possible without each of them, as well as the unmentioned Wiley staff behind the scenes.

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Introduction

This book is a complete SQL functions reference for all of the major RDBMS vendors in today’s market. Structured Query Language (SQL) is the standard language used to communicate with relational databases. SQL is a simple, English-like (yet powerful) language that allows the database user to effec-tively store, manipulate, and retrieve data from a database. Among the most robust features of SQL is its ability to mine data from a database and flexibly display that data in a format that suits the user’s exact needs. SQL functions comprise a huge part of the SQL language and play a critical role in determining what data is retrieved, how it is retrieved, and how it is to be displayed. Once you learn to query a database with SQL, learning how to intelligently use functions will allow you to quickly master the art of retrieving data from any relational database. This book will contribute to your mastery of effective data retrieval using SQL, regardless of the vendor implementation you are using.

The SQL implementations covered in this book include ANSI SQL, Oracle, Microsoft SQL Server, Sybase, IBM Universal Database (UDB) DB2, MySQL, and PostgreSQL. As a SQL programmer, you will find that there is a growing need to effectively use SQL functions, yet there are few resources to serve as an aid. You will also encounter the need to cross-reference different SQL implementations, at times having to integrate data between, say, Oracle and SQL Server. Migrations of data from one implementation to another is also very common in data warehousing environments, and as organizations make the commit-ment to go with another vendor’s relational database managecommit-ment system (RDBMS) to better support evolving business needs. This book is the necessary tool to facilitate expedient function referencing, cross-referencing between implementations, creating userdefined functions (UDFs), and providing tips and examples for applying the use of functions to real-world data-retrieval situations.

If you have purchased this book, thank you. We know that you will find this book to be an invaluable reference for SQL functions for all the major players in the RDBMS market. If you are considering this book, please take a minute to flip through this reference, making note of the reference material, the trail-ing chapters describtrail-ing real-world practical applications of SQL functions, and particularly Appendix A, which cross-references all the functions contained in this book by vendor. You should find this book to be thorough and inclusive of all functions currently available in each of the major RDBMS vendor implementations.

Who This Book Is For

This book is for the SQL programmer, and any software developer who has a need to effectively retrieve data from a relational database, or to integrate applications with RDBMS implementations. Database admin-istrators and other database users will also discover great value. This book is for readers of all levels, and has been organized in an easy-to-understand format that allows quick search and reference. This book is packed with realistic examples, allowing the reader to immediately apply SQL functions concepts to the job at hand.

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How This Book Is Organized

This book has been organized into four major sections for your convenience and ease of use. We have also included several appendixes for supplemental reference related to SQL functions. Following are brief descriptions.

Introduction to Functions

The introductory chapters in this book (Chapters 1–4) provide an overview of SQL, SQL built-in functions, UDFs, and major vendor implementations of RDBMS and SQL functions. These chapters are meant to serve as an introduction to SQL function architecture and concepts for those readers who need to increase their knowledge and sharpen their skills. Following is a breakdown of those introductory chapters:

❑ Chapter 1—Exploring popular SQL implementations ❑ Chapter 2—Concepts and architecture of functions

❑ Chapter 3—Comparison of SQL built-in functions by vendor ❑ Chapter 4—SQL procedural extensions and user-defined functions

Functions Reference by Vendor

Chapters 5–11 contain the primary reference material for built-in SQL functions for all of the major RDBMS vendors. Each chapter includes an introduction with SQL query syntax and a summary in addi-tion to the core reference material. Detailed examples are included with each and every funcaddi-tion, along with function syntax and detailed explanations. Reference chapters include thorough coverage of the fol-lowing vendor implementations.

❑ Chapter 5—ANSI SQL ❑ Chapter 6—Oracle ❑ Chapter 7—IBM DB2 UDB ❑ Chapter 8—SQL Server ❑ Chapter 9—Sybase ❑ Chapter 10—MySQL ❑ Chapter 11—PostgreSQL

Creating User-Defined Functions by Vendor

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❑ Chapter 12—ANSI SQL ❑ Chapter 13—Oracle ❑ Chapter 14—IBM DB2 UDB ❑ Chapter 15—SQL Server ❑ Chapter 16—Sybase ❑ Chapter 17—MySQL ❑ Chapter 18—PostgreSQL

Functions in Action

Chapters 19–27 contain valuable material showing functions “in action.” In other words, we have identi-fied several common instances in which SQL functions are used every day by most organizations. This content is more instructional versus a reference lookup, and reveals SQL function uses that are widely unknown to many database users. Topics in this section include the following:

❑ Chapter 19—Reporting and ad hoc queries ❑ Chapter 20—Using functions for migrating data ❑ Chapter 21—Using functions to feed a data warehouse

❑ Chapter 22—Using embedded functions and other advanced uses ❑ Chapter 23—Generating SQL with SQL and functions

❑ Chapter 24—Embedding SQL functions in an application ❑ Chapter 25—Empowering the query with functions and views

❑ Chapter 26—Understanding the impact of SQL functions on query and database performance ❑ Chapter 27—Utilizing useful queries from the system catalog (by vendor implementation)

Appendixes

Several appendixes have been included to offer quick access to SQL function-relevant material. Following is a breakdown of the appendixes:

❑ Appendix A—This includes a built-in function cross reference table and index, listing all func-tions covered in the book. You will quickly see the value of this resource because it allows you to quickly and easily locate functions supported by each vendor, compare coverage in other SQL implementations, and find similar functions in different implementations. This appendix is particularly useful for the programmer who deals with more than one RDBMS implementation.

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❑ Appendix E—This provides an Open Database Connectivity (ODBC) quick reference, showing how to establish an ODBC database connection via an application. ODBC is one of the most common methods for integrating an application and a database.

❑ Appendix F—This is a Java Database Connectivity (JDBC) quick reference, showing how to establish a JDBC database connection via an application. JDBC is another common method for integrating an application and a database.

❑ Glossary—This provides a listing of common database and SQL terminology.

How to Use This Book

This book was primarily created as a comprehensive SQL function reference book for the programmer, although we have included supplemental material to increase its value to you as the reader and database user. Following are our recommendations on how to use this book.

As a Reference

To use this book as a complete reference, you may find the following useful:

❑ Table of contents—This is best used to navigate to a high-level topic, particularly reference chapters for vendor-dependent SQL functions. The table of contents is also a good way to quickly navigate to a desired appendix, and to find introductory or trailing chapters with special-interest content.

❑ Index—This is best used to find a specific function based on function name or concept.

❑ Appendix A—This is best used to cross-reference all functions covered in this book. This appendix is particularly useful if you are dealing with multiple RDBMS versions.

❑ Flip method—The reference material in this book is organized both logically and alphabetically for the reader who likes to manually flip through the book.

For Understanding SQL Concepts

To aid in the understanding of SQL concepts, you may find the following useful:

❑ Introductory material—Read Chapters 1–4 sequentially to better understand SQL and the archi-tecture and concepts behind SQL functions.

❑ Function references—Each reference chapter (Chapters 5–18) can be read individually to grasp a better understanding of a specific SQL implementation. Each chapter includes an introduction, explanation of SQL query syntax, and summary. Additionally, the reference material is organized logically and written in a manner to facilitate reader comprehension.

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Conventions

To help you get the most from the text and keep track of what’s happening, we’ve used a number of con-ventions throughout the book.

Tips, hints, tricks, and asides to the current discussion are offset and placed in italics like this.

As for styles in the text:

❑ We highlight new terms and important words in italics when we introduce them. ❑ We show keyboard strokes like this: Ctrl+A.

❑ We show file names, URLs, and code within the text like so: persistence.properties.

❑ We present code in two different ways:

In code examples we highlight new and important code with a gray background.

The gray highlighting is not used for code that’s less important in the present context, or has been shown before.

Errata

We make every effort to ensure that there are no errors in the text or in the code. However, no one is per-fect, and mistakes do occur. If you find an error in one of our books, like a spelling mistake or faulty piece of code, we would be very grateful for your feedback. By sending in errata you may save another reader hours of frustration and at the same time you will be helping us provide even higher quality information.

To find the errata page for this book, go to http://www.wrox.comand locate the title using the Search box or one of the title lists. Then, on the book details page, click the Book Errata link. On this page you can view all errata that have been submitted for this book and posted by Wrox editors. A complete book list including links to each book’s errata is also available at www.wrox.com/miscpages/booklist.shtml.

If you don’t spot “your” error on the Book Errata page, go to www.wrox.com/contact/techsupport. shtmland complete the form there to send us the error you have found. We’ll check the information and, if appropriate, post a message to the book’s errata page and fix the problem in subsequent editions of the book.

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At p2p.wrox.comyou will find a number of different forums that will help you not only as you read this book, but also as you develop your own applications. To join the forums, just follow these steps:

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For More Information

For more information about this book, supplemental material, Wiley Publishing, and other useful books and resources, visit Wiley’s Web site at www.wiley.com.

For more information about the authors of this book, Perpetual Technologies, and additional database and SQL resources, visit the Perpetual Technologies Web site at www.perptech.com.

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Implementations

Any tour into the realm of writing SQL functions should begin with a solid foundation of the basic principles of SQL. In this chapter, we will be discussing the ins and outs of creating, querying, and modifying databases using basic SQL syntax. This chapter is the basis upon which we will build in the following chapters. This will help you unravel the mystery of using the power of built-in func-tions available across the various relational database management systems (RDBMS) platforms and to introduce new functionality into your applications by developing your own user-defined functions (UDFs).

Introduction to SQL

Structured Query Language (otherwise known as SQL and pronounced “SEE-kwul”) was first developed by IBM in the mid- to late 1970s for their DB2 platform RDBMS. At the time, its purpose was to provide a way in which the RDBMS could retrieve data in a declarative way. Declarative “programming” was a way in which the RDBMS developer could specify what data would be selected, inserted, updated, or deleted without having to necessarily know where the data was or how it was stored. That was the job of the RDBMS. The main goal of SQL was to provide the follow-ing functionality to the RDBMS:

❑ Query the database to retrieve the data stored therein.

❑ Update existing data within the database.

❑ Insert new data into the database.

❑ Remove unwanted data from the database.

❑ Add permissions to RDBMS objects (databases, tables, and so on).

❑ Modify a database’s structure.

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Oracle released the first commercial RDBMS that used SQL in 1978. Soon after that, in the mid-1980s, Sybase released its own RDBMS, SQL Server. In 1988, this was ported to OS/2 by Sybase and Microsoft, and eventually to Windows NT. In 1993, the partnership parted ways and Sybase eventually renamed their product Adaptive Server Enterprise (ASE)to differentiate it from the Microsoft version. However, since that time, Open Source RDBMS solutions such as MySQL and PostgreSQL have taken hold in the marketplace and are among the fastest growing. Even though all of these systems follow or attempt to follow the same base SQL implementation, each has its own unique characteristics and extensions that make it stand out from the rest.

Understanding the SQL Standard

The “standard” of SQL is laid out by both the American National Standards Institute (ANSI) and the International Standards Organization (ISO). It is fundamentally a set of base standards that, in theory, is the agreed-upon example of what the SQL syntax and logic in an RDBMS should be. The original ANSI stan-dard was put forth in 1986 and then later developed into ANSI SQL:1989 or, simply, SQL 89. The former version laid out a basic pattern of the following three separate ways in which SQL could be implemented:

❑ Embedded —This refers to embedding SQL statements within a program separate from the RDBMS instance. Patterns for this implementation were written to reflect the programming languages of the day (COBAL, FORTRAN, Pascal, and PL/1).

❑ Direct —The implementer could provide specific direct implementation of SQL to the developer.

❑ Module —Modules enable calls from procedures within programs and return a value to the calling program.

This baseline was further expanded with the release of ANSI 1992 or SQL 92, which included such things as connections to databases, dynamic SQL, and outer joins. This was in addition to establishing levels of compliance (entry, intermediate, and full) that the RDBMS system could tout to their user base. SQL:1999 again extended the standard by including more data types in the mix, such as arrays, user-defined types (UDTs), Boolean, BLOB, and CLOB. SQL:2003 expands upon the data types available, along with some new built-in functions.

However, it should be noted that the standards for core compliance have not been changed from the SQL:1999 version. This effectively means that anything that is SQL 99-compliant will automatically be SQL:2003-compliant as well. Therefore, it is important to understand that even though a specific RDBMS implementation may by SQL:2003-compliant, it does not mean that it has implemented all of the changes proposed within the new standard. In actuality, it has just prescribed to a set of core compliance stan-dards, and you will have to check the specific instance of your RDBMS documentation to see which parts have truly been implemented.

Over view of Vendor Implementations of SQL

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standard is something that every database should strive to emulate, each vendor implementation of that standard is unique and has nuances that the other implementations will not have. This section provides an overview of each of the six different RDBMS implementations discussed in this book to give you a good understanding of their backgrounds before going into the technical details of each implementation.

Oracle

Oracle is the market leader in the commercial RDBMS market. As mentioned in the previous section, Oracle released the first commercially available RDBMS in 1978. With the release of its commercial ver-sion 10g, Oracle claims SQL:2003 compliance, as well as a full set of features and tool sets for the devel-oper. In addition, Oracle provides several different editions that fit a wide variety of operating

environments (UNIX, Linux, and Windows) and levels of use.

IBM DB2 UDB

IBM created SQL for their DB2 database platform in the mid- to late 1970s. IBM is the world’s leading hardware vendor, and their DB2 database platform has evolved into their Universal Database line. As of this writing, the current version is 8.2, and they offer several different editions to fit a number of operat-ing platforms and uses.

Microsoft SQL Server and Sybase

As mentioned earlier, Sybase produced the original SQL Server and Microsoft later entered into a code-velopment agreement with them. Later in 1988, Microsoft ported the database from OS/2 over to their Windows platform. In 1993, the two companies discontinued their agreement and parted ways.

Since the split in 1993, Sybase has renamed their products Sybase Adaptive Server Enterpriseand Sybase IQ. Originally developed for the OS/2 environment, Sybase’s RDMS is now available for a wide variety of platforms, such as Windows, Linux, Solaris x86/64-bit, and Mac.

Microsoft is now the world’s largest software developer. SQL Server 2000 is now their flagship database version, and they will soon release SQL Server 2005 (its beta version is currently available). Microsoft touts the ease of use of their database system, rather than total ANSI compliance. They provide a feature-rich set of administration tools, but are limited to the Microsoft Windows platform. SQL Server’s most obvious difference from other SQL implementations is its use of Microsoft’s extension language T-SQL. In Microsoft’s version, there is no apparent difference to distinguish T-SQL from the standard version of SQL: they are treated as one and the same.

MySQL

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PostgreSQL

PostgreSQL (pronounced “Post-gres-Q-L”) was developed in 1986 at the University of California at Berkeley. Today, it is considered to be the most powerful of the available Open Source RDBMS packages. Initially, PostgreSQL was written to perform on a number of versions of the UNIX operating system. As of this writing, PostgreSQL is in version 8.0 Beta 4, and is available since the initial release of version 8.0 on Windows NT-based systems. Whereas MySQL was written to be fast, PostgreSQL was developed to be “full featured.” However, the trend has shifted with each subsequent release to make it faster.

Connecting to SQL Databases

To connect to an RDBMS, you must have two things: an SQL client and a CONNECTIONstatement. The SQL client acts as (or at least is perceived to be) a part of the specific SQL implementation. In addition, it also helps keep track of the state of all three parts of the connection instance: itself, the SQL agent, and the SQL server. Different vendors will have their own versions (even though the functionality is similar) of the SQL client. Oracle has SQL-PLUS and SQLPlus Worksheet, Microsoft had their own version in Query Analyzer, MySQL has MySQLGUI, and the list goes on. Once you have your particular client that matches your RDBMS of choice, connecting to a database is a rather simple matter. This is done by issu-ing the followissu-ing SQL command:

CONNECT TO <database_name>

If your SQL client is set up with a default database to connect to, then you can simply issue the default connection command, which is the following:

CONNECT TO DEFAULT

Please note that if there is no default database established for the SQL client, then an exception error will be thrown by the client because it will not be able to establish a connection. However, depending on which RDBMS system you have and how your security context is set up, after issuing the command, you will more often than not be challenged for a username/password combination to access the database itself.

Once you are connected to your particular database instance, you can change to another database by issuing another CONNECTstatement, naming the connection, and then issuing the SETstatement to move between your different named connections, as shown here:

CONNECT TO DATABASE1 AS FIRSTDB USER sa; CONNECT TO DATABASE2 AS SECONDDB USER sa; SET CONNECTION FIRSTDB;

// Now we are working with the first database... // SET CONNECTION SECONDDB;

// Now we are working with the second database.... //

Once you are finished working within your database(s), it is also necessary to disconnect from your ses-sion using the DISCONNECTstatement, as shown here:

DISCONNECT <connection_name>;

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ANSI SQL Data Types

The ANSI SQL standard also specifies different data types in which to hold your data. In general, each RDBMS implementation will vary from these as each uses its own unique set to provide some unique-ness to the environment. The basic set of SQL data types can be broken down into the categories shown in the following table.

Type

ANSI SQL Data Types

Boolean BOOLEAN

String CHAR

VARCHAR

Numeric NUMERIC

DECIMAL

DOUBLE PRECISION FLOAT

INTEGER REAL SMALLINT BIGINT

Date Time DATE

TIME TIMESTAMP

Since each RDBMS implementation differs, it is always best to refer to the documentation of your specific vendor to determine which data types it supports. The preceding table should merely serve as a guideline for some of the basic data types that are supported by the ANSI standard. Your particular vendor could have more or less, depending on the implementation. It is equally important to read the vendor descrip-tions of data types carefully, because, even though two vendors may provide data types with the same name, their precision and range may differ.

Creating SQL Databases

To create a new SQL database, you must issue the following command:

CREATE DATABASE <database_name>

This is the basic syntax for the CREATE DATABASE statement. There are plenty of optional clauses that can be used with the statement, but they differ from implementation to implementation. Clauses include those that specify everything for location of data files, database collation, and database state. It is best to check with your RDBMS systems documentation for the particular variance that they support.

Wrox SQL Functions Programmers Reference Apr 2005 ISBN 0764569015 pdf

Arie Jones

Ryan K. Stephens

Ronald R. Plew

Robert F. Garrett

Arie Jones

Ryan K. Stephens

Ronald R. Plew

Robert F. Garrett

Alex Kriegel

Joshua Stephens

Richard Bulley

Acknowledgments

Contents

Acknowledgments ix

Introduction xxxv

Chapter 1:

Exploring Popular SQL Implementations

1

Introduction to SQL

1

Understanding the SQL Standard

2

Overview of Vendor Implementations of SQL

2

Oracle

3

IBM DB2 UDB

3

Microsoft SQL Server and Sybase

3

MySQL

3

PostgreSQL

4

Connecting to SQL Databases

4

ANSI SQL Data Types

5

Creating SQL Databases

5

Querying SQL Databases

7

Manipulating Data in SQL Databases

9

Summary

11

Chapter 2: Functions: Concept and Architecture

13

What Is a Function?

13

Simple UNIX Shell Function Example

14

Simple SQL Function Example

15

ANSI SQL Functions

15

Built-in Functions

16

Executing Built-in Functions

17

Practical Uses of Functions

17

Creating, Compiling, and Executing a SQL Function

18

Passing Parameters by Value or by Reference

22

Scope of a Function

24

Better Security

25

Overloading

25

Classifying SQL Functions: Deterministic and Non-Deterministic Functions

27

Oracle

29

Microsoft SQL Server

30

Sybase