The Disturbed Buddha

Simple Observations of a Self-proclaimed Novice

A Visual Explanation of Different SQL JOINs

One of my standard interview questions to ask beginner- and intermediate-level developers who say that they know SQL is “Please explain a LEFT OUTER JOIN to me.” You’d be amazed how many people who “know SQL” trip over this. Understanding how to return proper sets of data from multiple tables is fundamental.

Jeff Atwood has a great post where he uses the concepts of data sets and Venn Diagrams to visually explain what each type of JOIN returns. Check it out:

http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html

Venn Diagram

December 20, 2013 Posted by | SQL, Uncategorized | Leave a comment