Hey SQL DBA's and developers, still having trouble trying to visualize joins and how they work? Well, give that part of your brain a rest and look at this article that uses Venn diagrams to make a visual representation of how joins work.
http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html
Many of my students have told me that this has helped them tremendously to get a better grasp on the concept and, admittedly, it has made my job alot easier :)
Now, certainly, there are some exceptions that cannot be expressed in this manner, and the analogy breaks down under careful examination. Please refrain from bombarding my inbox with all of the reaons that this analogy is flawed :) Most analogies are. But for those of you who are trying to get just the slightest notion of what a join does, this article is a great starting place to get your brain moving in the right direction.
And you can always come to my October class on T-SQL to have this clarified. Look forward to seeing you there!
- Peter Trast, SQL Expert; MCITP DBA, MCITP EA, MCT LinkIn with Peter
No comments:
Post a Comment