20 Database Design Practices

When designing database, you have choices to make. To work in the right direction and preventing regretting design decisions, I am using these best practices :

  1. Use consistent names. Well defined and consistent names for tables and columns (e.g. School, StudentCourse, CourseID ...).
  2. Use singular for table names (i.e. use StudentCourse instead of StudentCourses). Table represents a collection of entities, there is no need for plural names.
  3. Don’t use spaces for table names. Otherwise you will have to use ‘{‘, ‘[‘, ‘“’ etc. characters to define tables (i.e. for accesing table Student Course you'll write “Student Course”. StudentCourse is much better).
  4. Don’t use unnecessary prefixes or suffixes for table names (i.e. use School instead of TblSchool, SchoolTable etc.).
  5. Keep passwords as encrypted for security. Decrypt them in application when required.
  6. Use integer id fields for all tables. If id is not required for the time being, it may be required in the future (for association tables, indexing ...).
  7. Choose columns with the integer data type (or its variants) for indexing. varchar column indexing will cause performance problems.
  8. Use bit fields for boolean values. Using integer or varchar is unnecessarily storage consuming. Also start those column names with “Is”.
  9. Provide authentication for database access. Don’t give admin role to each user.
  10. Avoid “select *” queries until it is really needed. Use "select [required_columns_list]" for better performance.
  11. Use an ORM (object relational mapping) framework (i.e. hibernate, iBatis ...) if application code is big enough. Performance issues of ORM frameworks can be handled by detailed configuration parameters.
  12. Partition big and unused/rarely used tables/table parts to different physical storages for better query performance.
  13. For big, sensitive and mission critic database systems, use disaster recovery and security services like failover clustering, auto backups, replication etc.
  14. Use constraints (foreign key, check, not null ...) for data integrity. Don’t give whole control to application code.
  15. Document your database design with ER schemas and instructions. Lack of database documentation is evil. Also write comment lines for your triggers, stored procedures and other scripts.
  16. Use indexes for frequently used queries on big tables. Analyser tools can be used to determine where indexes will be defined. For queries retrieving a range of rows, clustered indexes are usually better. For point queries, non-clustered indexes are usually better.
  17. Database server and the web server must be placed in different machines. This will provide more security (attackers can’t access data directly) and server CPU and memory performance will be better because of reduced request number and process usage.
  18. Image and blob data columns must not be defined in frequently queried tables because of performance issues. These data must be placed in separate tables and their pointer can be used in queried tables.
  19. Normalization must be used as required, to optimize the performance. Under-normalization will cause excessive repetition of data, over-normalization will cause excessive joins across too many tables. Both of them will get worse performance.
  20. Spend time for database modeling and design as much as required. Otherwise saved(!) design time will cause (saved(!) design time) * 10/100/1000 maintenance and re-design time.

Happy new year!!

Gelukkig nieuwjaar! Stastny Novy Rok! Bonne année! Ein glückliches neues Jahr! Felice Anno Nuovo! Feliz año nuevo! Sawatdee Pi Mai! Srećna Nova godina! yeni yılınız kutlu olsun!

 

Launched my first Windows Phone application

1 van 7Currently I am using a Samsung Ativ-s with Windows Phone 8 on it. As a chess player I was always curious about the title match between Vishy Anand and his challenger Magnus Carlson. Magnus won victoriously and that’s good thing for the sport. What an exceptional chess player he is.

The problem was that I search in the dutch Windows App store I could find any chess related news app.

So I decided that it was time to start diving into Windows Phone development. Just a few days ago my Schaak Nieuws app got accepted!

If you’re interested, you can download the Schaak Nieuws app from the Windows Phone App Store for free. Please be so kind to give it a good review or contact me directly if something is wrong!

In January the Tata Steel Chess tournament will commence, you can check the latest news now directly on your Windows Phone!

Great AngularJS Fundamentals video

Heard about AngularJS? This client-side MVC framework from Google is written in Javascript and enables you to develop dynamic web applications in a mature and structural way. Dan Wahlin has put much effort in creating a great introduction to Angular JS.

 

 

Some related links:

  1. Dan Wahlin article about AngularJS Fundamentals in 60-ish Minutes
  2. Direct download of AngularJS demo code
  3. AngularJS in 60 minutes e-book – download it as PDF
  4. The AngularJS Magazine for the latest AngularJS news
  5. Angular seed project template for setting up a basic project structure