A Developer's Guide to Data Modeling for SQL Server: Covering SQL Server 2005 and 2008
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As database professionals, we are frequently asked to come into existing environments and “fix” existing databases. This is usually because of performance problems that application developers and users have uncovered over the lifetime of a given application. Inevitably, the expectation is that we can work some magic database voodoo and the performance problems will go away. Unfortunately, as most of you already know, the problem often lies within the design of the database. We often spend hours in meetings trying to justify the cost of redesigning an entire database in order to support the actual requirements of the application as well as the performance needs of the business. We often find ourselves tempering good design with real-world problems such as budget, resources, and business needs that simply don’t allow for the time needed to completely resolve all the issues in a poorly designed database.
What happens when you find yourself in the position of having to redesign an existing database or, better yet, having to design a new database from the ground up? You know there are rules to follow, along with best practices that can help guide you to a scalable, functional design. If you follow these rules you won’t leave database developers and DBAs cursing your name three years from now (well, no more than necessary). Additionally, with the advent of enterprise-level relational database management systems, it’s equally important to understand the ins and outs of the database platform your design will be implemented on.
There were two reasons we decided to write this book, a reference for everyone out there who needs to design or rework a data model that will eventually sit on Microsoft SQL Server. First, even though there are dozens of great books that cover relational database design from top to bottom, and dozens of books on how to performance-tune and write T-SQL for SQL Server, there wasn’t anything to help a developer or designer cover the process from beginning to end with the right mix of theory and practical experience. Second, we’d seen literally hundreds of poorly designed databases left behind by people who had neither the background in database theory nor the experience with SQL Server to design an effective data model. Sometimes, those databases were well designed for the technology they were implemented on; then they were simply copied and pasted (for lack of a more accurate term) onto SQL Server, often with disastrous results. We thought that a book that discussed design for SQL Server would be helpful for those people redesigning an existing database to be migrated from another platform to SQL Server.
We’ve all read that software design, and relational database design in particular, should be platform agnostic. We do not necessarily disagree with that outlook. However, it is important to understand which RDBMS will be hosting your design, because that can affect the capabilities you can plan for and the weaknesses you may need to account for in your design. Additionally, with the introduction of SQL Server 2005, Microsoft has implemented quite a bit of technology that extends the capabilities of SQL Server beyond simple database hosting. Although we don’t cover every piece of extended functionality (otherwise, you would need a crane to carry this book), we reference it where appropriate to give you the opportunity to learn how this functionality can help you.
Within the pages of this book, we hope you’ll find everything you need to help you through the entire design and development process—everything from talking to users, designing use cases, and developing your data model to implementing that model and ensuring it has solid performance characteristics. When possible, we’ve provided examples that we hope will be useful and applicable to you in one way or another. After spending hours developing the background and requirements for our fictitious company, we have been thinking about starting our own music business. And let’s face it—reading line after line of text about the various uses for a varchar data type can’t always be thrilling, so we’ve tried to add some anecdotes, a few jokes, and even a paraphrased movie quote or two to keep it lively.
Writing this book has also been an adventure for both of us, in learning how the publishing process works, learning the finer details of writing for a mass audience, and learning that even though we are our own worst critics, it’s hard to hear criticism from your friends, even if they’re right; but you’re always glad that they are.