Beginning Visual Basic 2005 Databases. Thearon Willis

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1 Beginning Visual Basic 2005 Databases Thearon Willis

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3 Beginning Visual Basic 2005 Databases

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5 Beginning Visual Basic 2005 Databases Thearon Willis

6 Beginning Visual Basic 2005 Databases Published by Wiley Publishing, Inc Crosspoint Boulevard Indianapolis, IN Copyright 2006 by Wiley Publishing, Inc., Indianapolis, Indiana Published simultaneously in Canada ISBN: X Manufactured in the United States of America B/QR/RR/QV/IN Library of Congress Cataloging-in-Publication Data: Willis, Thearon. Beginning Visual Basic 2005 databases / Thearon Willis. p. cm. Includes bibliographical references and index. ISBN-13: (paper/website) ISBN-10: X (paper/website) 1. Web databases. 2. Client/server computing. 3. Microsoft Visual BASIC. I. Title. QA76.9.W43W dc No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) , fax (978) Requests to the Publisher for permission should be addressed to the Legal Department, Wiley Publishing, Inc., Crosspoint Blvd., Indianapolis, IN 46256, (317) , fax (317) , or online at LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: THE PUBLISHER AND THE AUTHOR MAKE NO REP- RESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CON- TENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CRE- ATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CON- TAINED HEREIN MAY NOT BE SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOR THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A POTENTIAL SOURCE OF FUR- THER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFOR- MATION THE ORGANIZATION OR WEBSITE MAY PROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ. For general information on our other products and services please contact our Customer Care Department within the United States at (800) , outside the United States at (317) or fax (317) Trademarks: Wiley, the Wiley logo, Wrox, the Wrox logo, Programmer to Programmer, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates, in the United States and other countries, and may not be used without written permission. Visual Basic is a registered trademark of Microsoft Corporation in the United States and/or other countries. All other trademarks are the property of their respective owners. Wiley Publishing, Inc., is not associated with any product or vendor mentioned in this book. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

7 About the Author Thearon Willis is a senior consultant with over 20 years of programming experience. He started writing applications using the Basic language in 1980 and later moved on to Visual Basic and finally to Visual Basic.Net. He began working with databases in 1987 and has been hooked on writing database applications ever since. He has experience with SQL Server, Oracle, and DB2 but works with SQL Server on a daily basis. Thearon has programmed in several other languages, some of which include C++, Assembler, Pascal, and COBOL. However, he enjoys Visual Basic.Net the best as it provides the features needed to quickly build Windows and Web applications as well as components and Web Services. He currently develops intranet applications, Web Services, and server-side and client-side utilities using Visual Basic.Net. Most of these applications and utilities are database-driven and make use of XML and XSL. Thearon lives with his wife, Margie, and daughter, Stephanie, in the Raleigh, North Carolina area.

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9 Acquisitions Editor Katie Mohr Development Editor Sydney Jones Technical Editor Todd Meister Production Editor Pamela Hanley Project Coordinator Michael Kruzil Credits Copy Editor Nancy Rapoport Editorial Manager Mary Beth Wakefield Vice President & Executive Group Publisher Richard Swadley Vice President and Publisher Joseph B. Wikert Proofreading and Indexing TECHBOOKS Production Services

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11 For my dearest love

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13 Contents Acknowledgments Introduction xvii xix Chapter 1: Databases 1 Access Databases 2 Database file 2 Tables 2 Queries 3 SQL Server Databases 3 Data files 4 Log files 7 Oracle Databases 7 Data files 8 Redo log files 10 Control files 10 Temp files 10 Password files 10 Relational Database Design 10 Normalization 12 Building the Case Study Databases 15 Access schema 15 SQL Server schema 20 Oracle schema 25 Summary 30 Chapter 2: An Introduction to ADO.NET 31 ADO.NET Overview 31 ADO.NET architecture 32 ADO.NET components 33 Connection Class 37 Common constructors 37 Opening a connection 39 Closing a connection 39

14 Contents Command Class 40 DataAdapter Class 41 DataReader Class 43 Summary 44 Exercises 45 Exercise 1 45 Exercise 2 45 Chapter 3: Visual Studio 2005 Data Wizards 47 Data Access Components 47 DataSet 48 DataGridView 48 BindingSource 49 BindingNavigator 49 TableAdapter 49 Data Binding 49 Summary 56 Exercises 57 Exercise 1 57 Exercise 2 57 Chapter 4: Basic SQL 59 INSERT Statement 59 SELECT Statement 65 UPDATE Statement 67 DELETE Statement 69 Summary 71 Exercises 72 Exercise 1 72 Exercise 2 72 Chapter 5: SQL and Queries for Access 73 Dynamic Connections 73 Building a connection string 74 Opening, closing, and checking connection state 75 In-Line SQL 81 Summary 104 Exercises 105 Exercise Exercise xii

15 Contents Chapter 6: Selecting Data in Access 107 Building the Time Tracker Application 107 Implementing SQL Queries 109 Summary 121 Exercises 121 Exercise Exercise Chapter 7: Inserting, Updating, and Deleting Data in Access 123 OleDbCommand Object 123 Group Queries 136 Summary 154 Exercises 155 Exercise Exercise Chapter 8: Migrating Data from Access 157 Dynamic Connections 157 SQL Statement Parameters 167 Summary 177 Exercises 178 Exercise Exercise Chapter 9: Stored Procedures and Views for SQL Server and Oracle 179 Stored Procedures 180 Oracle packages 182 Views 205 Creating a view 207 Summary 232 Exercises 233 Exercise Exercise xiii

16 Contents Chapter 10: Building Business Logic and Data Access Components 235 Distributed Application Architecture 236 Design Goals of the Wrox Components 237 Designing the data access component 237 Designing the business logic component 238 Design overview 238 Summary 298 Exercise 299 Chapter 11: Inserting Data 301 Validating Data in the Business Logic Component 301 Handling empty strings and NULL values 302 Validating string data 303 Stored Procedures That Insert Data 339 Local variables 339 Error checking and raising errors 340 Conditional logic 341 Transactions 343 Cursors 344 Summary 363 Exercises 364 Exercise Exercise Chapter 12: Selecting Data 365 Column Aliases 365 Table Aliases 366 Concatenation 367 Joins 368 Inner or natural join 368 LEFT OUTER JOIN 369 Summary 434 Exercises 435 Exercise Exercise xiv

17 Contents Chapter 13: Updating Data 437 Stored Procedure Logic 437 Updating Timesheets 458 Summary 478 Exercises 479 Exercise Exercise Chapter 14: Accessing Data in ASP.NET 481 Selecting and Displaying Data 481 Web Form DataGrid Control 496 Summary 530 Chapter 15: Creating a Web Service 533 Design Goal 533 Date Functions 534 Current week ending date 535 First day of the month date 536 First day of the quarter 536 First day of the year 537 Web Services 556 Summary 568 Chapter 16: Accessing a Web Service 571 Referencing a Web Service in a Windows Application 571 Referencing a Web Service in a Web Application 580 Summary 601 Appendix A: Data Type Cross-Reference 603 Appendix B: Time Tracker Project UI 607 Building an Outlook Style Interface 607 Admin form 607 TimeSheet form 634 Login form 639 xv

18 Contents About form 641 MainEntry class 643 AssemblyInfo file 643 App.config file 644 WDABase class 644 Admin form code 648 TimeSheet form code 664 About form code 665 Appendix C: Exercise Solutions 667 Index 697 xvi

19 Acknowledgments As always, I want to thank my wife, Margie, and my daughter, Stephanie, for the patience they have shown while I write another book. Without their love and support, none of this would be possible.

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21 Introduction This book teaches Visual Basic 2005 developers the concepts and skills necessary to write VB 2005 database applications that can be used throughout their enterprises. Although the book touches on database design concepts, its focus is on using ADO.NET to access and manipulate data in relational databases. This book covers all data providers in ADO.NET briefly, but focuses on using the OleDb Data Provider for accessing Access databases, the SQL Data Provider for accessing SQL Server databases, and the Oracle Data Provider for accessing Oracle databases. Most of the examples in this book involve writing database applications for SQL Server and Oracle. You will learn how to use queries, views, and stored procedures to efficiently access and manipulate data from your applications. I provide examples and instruction on accessing data from Windows applications, ASP.NET applications, and Web Services. You ll also be exposed to more advanced concepts, such as writing business logic components and data access components, as well as how to read and write data from the Windows Registry. You will also learn how to encrypt and decrypt data using the.net encryption classes and how to hash passwords to further secure your access to your data. Who Is This Book For This book was designed for the developer who wants to learn how to write database applications using Visual Basic 2005 and back-end databases such as Microsoft Access, Microsoft SQL Server, and Oracle. There are two kinds of developers for whom this book is ideal: The beginning VB 2005 developer who already has some experience with Visual Basic 2005 developing Windows and ASP.NET applications. You ve read Beginning VB 2005 and are ready to learn database programming using VB Congratulations, you ve made a great choice and will learn the skills and concepts necessary to write efficient database applications. The experienced VB 2005 developer who is new to database programming. You ve also made a great choice, as you will hone your VB 2005 skills while you learn the skills and concepts necessary to write efficient database applications. What This Book Covers The ADO.NET classes offer a lot of features and functionality, much more than one book can cover in detail. This is especially true given all of the overloaded operators and methods available in these classes. However, the goal of this book is to teach you the concepts for efficiently accessing and manipulating data in enterprise applications. A brief review of database design concepts will help you understand relational database design.

22 Introduction ADO.NET is covered thoroughly so that you can get a firm grasp on this important data access technology in the.net Framework. Hands-on examples and Try It Out exercises are provided to help you put into practice the topics that you read about. This book is not intended to be used as a reference but as a teaching tool on building database applications using Visual Basic To that end, this book walks you through the process of building the various pieces of a single application chapter by chapter. Chapter 1 provides an overview of the components that make up Access, SQL Server, and Oracle databases as well as a refresher on relational database design and normalization. Chapters 2 and 3 provide an overview of ADO.NET and the data wizards available in Visual Studio Chapters 4 through 7 give you hands-on experience writing queries in Access and executing Access queries in your VB 2005 applications. Chapters 8 through 13 give you hands-on experience writing stored procedures and views in both SQL Server and Oracle, and executing those stored procedures and views from your VB 2005 application. You also build and enhance a business logic component and data access component starting in Chapter 10. Chapter 14 shows you how to use your business logic and data access components in an ASP.NET application to display and update data in your back-end databases. Chapter 15 shows you how to create a Web Service that also uses your business logic and data access components to produce report data. Finally, Chapter 16 shows you how to access your Web Service from both a Windows and Web application. What You Need to Run the Examples The following list describes the software components that you will need to complete the Try It Out exercises in each chapter. All chapters: Visual Studio 2005 Standard, Professional or Team System edition Chapters 3 through 8: Microsoft Office (2000, XP, or 2003 editions) or Microsoft Access (2000, XP, or 2003 editions) Chapter 3 and Chapters 8 through 16: You will need access to SQL Server 2005 or Oracle 10g installed locally on your machine or on your network. Conventions This book uses several different styles of text and layout to help differentiate between the different kinds of information. Here are examples of the styles used and an explanation of what they mean. xx

23 Introduction Try It Out How Do They Work? 1. Each step has a number. 2. Follow the steps. 3. Then read the How It Works section that follows to find out what s going on. These notes hold important, not-to-be-forgotten, mission-critical details that are directly relevant to the surrounding text. Bullets appear indented, with each new bullet marked as follows: Important words are in italics. Text you are required to type is in bold. Code has several styles. If I am talking about a word in the text for example, when discussing a For...Next loop it s in this font. If it s a block of code that can be typed as a program and run, then it s also in a gray box: Private Sub mnuhelpabout_click(byval sender As Object, _ ByVal e As System.EventArgs) Handles mnuhelpabout.click End Sub Dim objabout As New About objabout.showdialog(me) objabout = Nothing Sometimes you ll see code in a mixture of styles, like this: Private Sub mnuhelpabout_click(byval sender As Object, _ ByVal e As System.EventArgs) Handles mnuhelpabout.click End Sub Dim objabout As New About objabout.showdialog(me) objabout.dispose() objabout = Nothing In cases like this, the code with a white background is code you are already familiar with; the line highlighted in gray is a new addition to the code since you last looked at it. Customer Support We always value hearing from our readers, and we want to know what you think about this book: what you liked, what you didn t like, and what you think we can do better next time. You can send us your comments either by returning the reply card in the back of the book or by to feedback@wrox.com. Please be sure to mention the book title in your message. xxi

24 Introduction How to download the sample code for the book When you visit the Wrox site (wrox.com) simply locate the title through our Search facility or by clicking the Download Code link at the top of the main page; then find the book in the title list. Click the HTTP or FTP link for the book to download the code. The files that are available for download from our site have been archived using WinZip. When you have saved the attachments to a folder on your hard drive, you need to extract the files using a decompression program such as WinZip or PKUnzip. When you extract the files, the code is usually extracted into chapter folders. When you start the extraction process, ensure that your software (WinZip or PKUnzip) is set to use folder names. Errata We ve made every effort to ensure that there are no errors in the text or in the code. However, no one is perfect and mistakes do occur. If you find an error in one of our books, such as a spelling mistake or a faulty piece of code, we would be very grateful for feedback. By sending in errata, you may save another reader hours of frustration, and, of course, you will be helping us provide even higher quality information. Simply the information to support@wrox.com; your information will be checked and, if correct, posted to the errata page for that title, or used in subsequent editions of the book. To find errata on the Web site, go to wrox.com and simply locate the title through our Advanced Search or title list or by going to the Help Center using the link at the bottom of the main page. Click the View Errata link, which is to the right of the book s title. support If you wish to directly query a problem in the book with an expert who knows the book in detail, then support@wrox.com with the title of the book and the last four numbers of the ISBN in the subject field of the . A typical should include the following things: The title of the book, the last four digits of the ISBN (894X), and the page number of the problem in the Subject field Your name, contact information, and the problem in the body of the message We won t send you junk mail. We need the details to save your time and ours. When you send an message, it will go through the following chain of support: xxii Customer support: Your message is delivered to our customer support staff, who are the first people to read it. They have files on most frequently asked questions and will answer anything general about the book or the Web site immediately. Editorial: Deeper queries are forwarded to the technical editor responsible for that book. They have experience with the programming language or particular product, and are able to answer detailed technical questions on the subject. The authors: Finally, in the unlikely event that the editors cannot answer your problem, they will forward the request to the author. We do try to protect authors from any distractions to their writing; however, we are quite happy to forward specific requests to them. All Wrox authors help with the support on their books. They will the customer and the editor with their response, and again all readers should benefit.

25 Introduction The Wrox support process can offer support only for issues that are directly pertinent to the content of our published title. Support for questions that fall outside the normal scope of a book s support is provided via the community lists of our forum. p2p.wrox.com For author and peer discussion, join the P2P forums. Our unique system provides programmer-toprogrammer contact on mailing lists, forums, and newsgroups, all in addition to our one-to-one support system. If you post a query to P2P, you can be confident that it is being examined by the many Wrox authors and other industry experts who are present on our mailing lists. At p2p.wrox.com you will find a number of different lists that will help you, not only while you read this book, but also as you develop your own applications. Particularly appropriate to this book are the Visual Basic and VBA forums, the Database forums, and the DotNet forums. To subscribe to a forum, just follow these steps: 1. Go to 2. Register using the Register link from the left menu bar or log in if you are already a member. 3. Navigate to the appropriate forum. 4. Click the Subscribe to This Forum link for the forum you wish to join. Why this system offers the best support You can choose to join the mailing lists, or you can receive them as a weekly digest. If you don t have the time, or facility, to receive the mailing list, you can search our online archives. Junk and spam mail is deleted and your own address is protected by the unique Lyris system. Queries about joining or leaving lists, and any other general queries about lists, should be sent to listsupport@p2p.wrox.com. xxiii

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27 Beginning Visual Basic 2005 Databases

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29 1 Databases Most Visual Basic 2005 applications that you write use data in some form or fashion. Where you retrieve that data from depends on what your application is doing. One of the most common types of applications that you are likely to write is a database application, which retrieves and processes data from a database. Although there are different kinds of databases and different manufacturers, the databases that you are most likely to encounter are Microsoft Access, Microsoft SQL Server, and Oracle. This chapter explores the components that make up each of these common databases at a high level to help you gain a better understanding of how they work. To help you understand how databases are put together, you look also at relational database design. This topic describes the relationships between the different tables in your database and how they can be designed for optimal performance. At the end of the chapter, you build the sample databases that are used throughout the rest of this book. You ll be using these databases to perform the Try It Out exercises in each of the chapters. In this chapter, you: Learn which components make up a Microsoft Access database Learn which components make up a Microsoft SQL Server database Learn which components make up an Oracle database Learn about relational database design Build the sample databases used throughout the rest of this book

30 Chapter 1 Access Databases Access databases are common and can be found on most computers, especially if the sample databases were installed along with Microsoft Access as a standalone product or as part of Microsoft Office. People use Access databases for a variety of reasons but mainly because they are standalone databases, meaning that you can create an Access database and then send that database to someone else who, if he or she has Microsoft Access installed, can open and use your database. These databases are easy to use, and Access provides many wizards to help you create a functional database in no time at all. The database engine for Access is the Microsoft Access program MSACCESS.EXE. This database engine can create, open, and edit Access databases and manage the components that make up the database. The database engine is responsible for all the work that controls the database and the data contained in it. You can run this program by clicking Start on the taskbar and then clicking Run. In the Run dialog box, enter MSACCESS and click OK. Microsoft Access starts, and depending on which version of Microsoft Access you have, you may be prompted with a dialog box to open or create a new database. The bottom line is that you can see the database engine at work and the user interface that it provides. Although an Access database may look simple at first glance, it contains a lot of components, typically referred to as objects. All you see as a user is a database file that you can copy and distribute through a variety of channels. The brains behind the actual database itself is the database engine. In this section, you explore some components that make up an Access database to gain a deeper understanding and appreciation for the complexities that make up an Access database. Database file An Access database consists of one complex file that stores the various objects that make up the database. You have probably seen the classic sample database Northwind.mdb. When you open this database, you can view the tables, queries, forms, and reports. These are some of the objects contained in this database file and are controlled by the database engine. Access database files have an.mdb file extension and each database can contain tables, queries, forms, reports, pages, macros, and modules, which are referred to as database objects. That s a lot of information in one large file, but Microsoft Access manages this data quite nicely. Forms, reports, pages, macros, and modules are generally used to enable users to work with and display data contained in the database. You will be writing Visual Basic 2005 applications to do this, so the only database objects you re really concerned about at the moment are tables and queries. Tables A table contains a collection of data, which is represented by one or more columns, and one or more rows of data. Columns are typically referred to as fields in Microsoft Access, and the rows are referred to as records. Each field in a table represents an attribute of the data stored in that table. For example, a field named First Name would represent the first name of an employee or customer. This field is an attribute of an employee or customer. Records in a table contain a collection of fields that form a complete record of information about the data stored in that table. For example, suppose a table contains two fields, First 2