Browsing articles tagged with " Database Design"

How Deep is My Non-Love? Nested Dependencies and Overly Complex Design

Dec 4, 2017   //   by Karen Lopez   //   Blog, Data Modeling, Database, Database Design, SQL Server, WTF  //  No Comments

Relational databases have this nifty concept of objects (just things, not code objects) being dependent upon other things.  Sometimes those dependencies exist due to foreign key constraints, others via references to other things.  One example of the latter can be found in VIEWs.  A database VIEW is an object that references TABLEs or other VIEWS.  Of course, if that VIEW references other VIEWs, then that view must reference TABLEs or another VIEW.  And it’s that or another VIEW that can get modelers into trouble.

I reviewed a database design that had massively dependent VIEWs.  How did I know that? I used a proper data modeling tool to look at all the dependencies for one central VIEW.  And this is what my data modeling tool showed me:

Data Model with hundreds of dependencies (lines) between a handful of objects (squares)

That diagram shows how ONE VIEW is related to a whole bunch of other VIEWs and TABLEs in that design.  In reviewing the model, I saw that many of the VIEWs appeared to be duplicates or had very high overlap of content with other VIEWs. 

How do VIEWs Like This Happen?

There are many reasons one would created a nested VIEW.  Like anything in a hierarchy, you could have objects that could be used independently and as part of a group on a regular basis.  But that only explains one level of a VIEW hierarchy (nest).   What about VIEWs that are nested dozens are levels deep?  And why would a database have such a complex design around one VIEW?  These are the most common reasons I run into bad practices with VIEWs:

  • Designers who don’t understand the massive performance loss for massively nested VIEWS
  • Designers who design for theory, not for real world data stories
  • Designers who have no idea they are referencing another VIEW when they design their VIEW
  • Designers who are following a worst practice of creating a VIEW for every report and every window in an application
  • Designers who don’t collaborate with other designers and create their own set of VIEWs and dependencies
  • Designers who are compensated for doing work fast and not well
  • Designers who use DDL to do design, therefore never seeing the complexity of their designs
  • Data Governance policies that let anyone create objects in a database
  • A team environment were “everyone is a generalist”.

I could go on.  While I can’t go into details here, in my review I recommended complete refactoring of this overly complex design.  It is my guess this complexity was contributing to performance problems experienced in this application.  I also recommended that professional designer was used to refactor other issues with the database design.  I have no idea if this happened.  But I doubted that this application was going to meet its large scale web application goals.

Why Am I Sharing This?

Because so many design issues I find in reviews have the same causes for performance and data quality issues I’ve listed above.  I find that not using a real data modeling or design tool is the main contributing factor.  There’s a reason why physical world architects and engineers use drawings and architectural diagrams. Models are also how they make modifications successful to the items they build.

Yes, physical objects are different than software/application/database objects. My position is that these latter objects need models at least as much as buildings and devices do.  We need tools to reverse engineer objects, to view the dependencies, to search, and to assess.  In other words, to model.  Engineering data solutions requires engineering tools like data modeling tools.  And, yes, data engineers to understand how to use those tools and how to model out the unnecessary complexity.

The Tricky Part of Doing Tricky Things in your Data Model – SQL Saturday Phoenix

Apr 16, 2016   //   by Karen Lopez   //    //  No Comments

SQL Sat PHX logo

We’ve mastered the basics of data modeling and data modeling patterns, but what happens when you or a teammate wants to use this one weird trick to improve on the data model and the resulting database design? Have you just discovered a brilliant new trick that no one else has ever thought of? Or will your new design cost you more, take on more risk and cause all kinds of pain for both IT and your business users?

We’ll look at a few tricks that we’ve seen in our database design review and show you how they work and talk about the trade offs for using them. You’ll learn about:

Building a database engine inside your database
Designing before understanding your business model
Dealing with data structures that don’t do well in RDBMSs
Optimizing the developer versus the data or the app
Using design patterns that don’t reflect modern architectures and tools
…and a lot more

The Key to Keys – SQL Sat Huntington Beach

Apr 2, 2016   //   by Karen Lopez   //    //  No Comments

SQL Saturday HB logo

 

So many of us have learned database design approaches from working with one database or data technology. We may have used only one data modeling or development tool. That means our vocabularies around identifiers and keys tend to be product specific. Do you know the difference between a unique index and a unique key? What about the difference between RI, FK and AK?

These concepts span data activities and it’s important that your team understand each other and where they, their tools and approaches need to support these features.

We’ll look at the generic and proprietary terms for these concepts, as well as where they fit in the database design process. We’ll also look at implementation options in SQL Server and other DBMSs.

The Key to Keys: NTSSUG 17 March

Mar 17, 2016   //   by Karen Lopez   //    //  No Comments

Level: Intermediate

So many of us have learned database design approaches from working with one database or data technology. We may have used only one data modeling or development tool. That means our vocabularies around identifiers and keys tend to be product specific. Do you know the difference between a unique index and a unique key? What about the difference between RI, FK and AK? These concepts span data activities and it’s important that your team understand each other and where they, their tools and approaches need to support these features. We’ll look at the generic and proprietary terms for these concepts, as well as where they fit in the database design process. We’ll also look at implementation options in SQL Server and other DBMSs.

I’ll be speaking about keys: primary keys, surrogate keys, clustered keys, GUIDs, SEQUENCEs, alternate keys…well, there’s a lot to cover about such a simple topic.  The reason I put this presentation together is I see a lot of confusion about these topics. Some of it’s about terminology (“I can’t find anything about alternate keys in SQL Server…what the heck is that, anyway”), some of it is misunderstandings (“what do you mean IDENTITIES aren’t unique! of course they are…they are primary keys!”), some of it is just new (“Why the heck would anyone want to use a SEQUENCE?”).

The Key to Keys at the North Texas SQL Server User Group – 17 March

Mar 15, 2016   //   by Karen Lopez   //   Blog, Data Modeling, Database, Database Design, DLBlog, Speaking, SQL Server  //  No Comments

I’m visiting Dallas this week to speak at the North Texas SQL Server User Group this Thursday.  I’ll be speaking about keys: primary keys, surrogate keys, clustered keys, GUIDs, SEQUENCEs, alternate keys…well, there’s a lot to cover about such a simple topic.  The reason I put this presentation together is I see a lot of confusion about these topics. Some of it’s about terminology (“I can’t find anything about alternate keys in SQL Server…what the heck is that, anyway”), some of it is misunderstandings (“what do you mean IDENTITIES aren’t unique! of course they are…they are primary keys!”), some of it is just new (“Why the heck would anyone want to use a SEQUENCE?”).

We’ll be chatting about all these questions and more on Thursday, 17 March at the Microsoft venue in Irving, Texas starting at 6PM.

Attendance is free, but you need to register at http://northtexas.sqlpass.org/ to help organizers plan for the event.

Don’t worry if you don’t know about SQL Server or don’t use it: this presentation will focus on some SQL Server specific features, but the discussion is completely portable to other DBMSs.

So many of us have learned database design approaches from working with one database or data technology. We may have used only one data modeling or development tool. That means our vocabularies around identifiers and keys tend to be product specific. Do you know the difference between a unique index and a unique key? What about the difference between RI, FK and AK? These concepts span data activities and it’s important that your team understand each other and where they, their tools and approaches need to support these features. We’ll look at the generic and proprietary terms for these concepts, as well as where they fit in the database design process. We’ll also look at implementation options in SQL Server and other DBMSs.

Hope to see you there!

Database Design Throwdown – Austin SQLSaturday

Jan 30, 2016   //   by Karen Lopez   //    //  No Comments

Database Design Throwdown

Speaker(s):  Karen Lopez Thomas LaRock

Duration: 60 minutes

Track: Application & Database Development

Everyone agrees that great database performance starts with a great database design. Unfortunately, not everyone agrees which design options are best. Data architects and DBAs have debated database design best practices for decades. Systems built to handle current workloads are unable to maintain performance as workloads increase.Attend this new and improved session and join the debate about the pros and cons of database design decisions. This debate includes topics such as logical design, data types, primary keys, indexes, refactoring, code-first generators, and even the cloud. Learn about the contentious issues that most affect your end users and how to avoid them.

SQLSaturdays are free to attend, usually with an option to pay for lunch if you’d like.

 

 

 

Database Design Throwdown, Texas Style

Jan 21, 2016   //   by Karen Lopez   //   Blog, Data, Data Modeling, Database, Database Design, DLBlog, Events, Fun, Snark, Speaking, SQL Server  //  3 Comments

SQLSaturday #461 - Austin 2016

It’s a new year and I’ve given Thomas LaRock (@@sqlrockstar | blog ) a few months to recover and ramp up his training since our last Throwdown.  The trophies from all my wins are really cluttering my office and I feel back that Tom has not yet had a chance to claim victory.  So we will battling again in just a few days.

I’ll be dishing out the knowledge along with a handkerchief for Tom to wipe up his tears at SQL Saturday #461 Austin, TX on 30 January 2016.  This full day community-driven event features real database professionals giving free presentations on SQL Server and Data Platform topics.  All you need to do is register (again, it’s free) before all the tickets are gone.

Database Design Throwdown

Speaker(s):  Karen Lopez Thomas LaRock

Duration: 60 minutes

Track: Application & Database Development

Everyone agrees that great database performance starts with a great database design. Unfortunately, not everyone agrees which design options are best. Data architects and DBAs have debated database design best practices for decades. Systems built to handle current workloads are unable to maintain performance as workloads increase.Attend this new and improved session and join the debate about the pros and cons of database design decisions. This debate includes topics such as logical design, data types, primary keys, indexes, refactoring, code-first generators, and even the cloud. Learn about the contentious issues that most affect your end users and how to avoid them.

One of the other great benefits of attending these events is that you get to network with other data professionals who are working on project just like yours…or ones you will likely work on at some point.

Join us an other data pros to talk about data, databases and projects. And make sure you give a #datahug to Tom after the Throwdown. He’s gonna need it.

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