Defensive Database Programming

Inside this book, you will find dozens of practical, defensive programming techniques that will improve the quality of your T-SQL code and increase its resilience and robustness.

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The goal of Defensive Programming is to produce resilient code that responds gracefully to the unexpected. To the SQL Server programmer, this means T-SQL code that behaves consistently and predictably in cases of unexpected usage, doesn’t break under concurrent loads, and survives predictable changes to database schemas and settings. Inside this book, you will find dozens of practical, defensive programming techniques that will improve the quality of your T-SQL code and increase its resilience and robustness.

Defensive Database Programming By Alex Kuznetsov

Download the free PDF. 

The book is available to buy from Amazon.com and Amazon.co.uk.

Why read this book?

Resilient T-SQL code is code that is designed to last, and to be safely reused by others. The goal of defensive database programming, the goal of this book, is to help you to produce resilient T-SQL code that robustly and gracefully handles cases of unintended use, and is resilient to common changes to the database environment.

Too often as developers, we stop work as soon as our code passes a few basic tests to confirm that it produces the ‘right result’ in a given use case. We do not stop to consider what other possible ways in which the code might be used in the future, or how our code will respond to common changes to the database environment, such as a change in the database language setting, or a change to the nullability of a table column, and so on.

In the short-term, this approach is attractive; we get things done faster. However, if our code is designed to be used for more than just a few months, then it is very likely that such changes can and will occur, and the inevitable result is broken code or, even worse, code that silently starts to behave differently, or produce different results. When this happens, the integrity of our data is threatened, as is the validity of the reports on which critical business decisions are often based. At this point, months or years later, and long after the original developer has left, begins the painstaking process of troubleshooting and fixing the problem.

Would it not be easier to prevent all this troubleshooting from happening? Would it not be better to spend a little more time and effort during original development, to save considerably more time on troubleshooting, bug fixing, retesting, and redeploying?

This is what defensive programming is all about: we learn what can go wrong with our code, and we proactively apply this knowledge during development. This book is filled with practical, realistic examples of the sorts of problems that beset database programs, including:

  • Changes in database objects, such as tables, constraints, columns, and stored procedures.
  • Changes to concurrency and isolation levels.
  • Upgrades to new versions of SQL Server.
  • Changes in requirements.
  • Code reuse.
  • Problems causing loss of data integrity.
  • Problems with error handling in T-SQL.

In each case, it demonstrates approaches that will help you understand and enforce (or eliminate) the assumptions on which your solution is based, and to improve its robustness. Ultimately, the book teaches you how to think and develop defensively, and how to proactively identify and eliminate potential vulnerabilities in T-SQL code.

Nikos Vaggalis at I Programmer called it ‘an indespensable guide’. See his review here.

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  • Johnm

    Looking forward to reading!
    Alex, it was a pleasure to meet you at the Chicago SQL Saturday. I wish we could have chatted more. I eagerly look forward to reading your book!

  • RGerald

    Defensive Database Programming
    When will the physical book be available? I’ve been waiting to buy a copy.

    Rand

  • alalani

    Chi-SSWUG
    Alex,
    It was nice meeting you yesterday at this user group. Your presentation about defensive and resilient programming totally made sense. Some were eye-openers such as difference between SET and SELECT. Also thanks for giving me your book. I was looking for link “defensive_code.zip” and could not find it. Please send me the current link to download the codes in the book.
    Thanks
    Ameena

  • roac

    A little feedback
    I really appreciate your book, but there is a small point that I’d like to point out. Handling of special characters are covered in “Defending Against Cases of Unintended Use”, but unfortunately _ (underscore) is forgotten. It does only match a single character, but it may still give an uninteded result.