So many times I have been asked for help with a query, where the questoin really comes down to the understanding of the difference between INNER and LEFT or RIGHT JOINs. I created this poster a few years ago and I keep it posted on the wall at the office. This way when I am trying to explain JOIN types, I just refer to the poster.
I have created the poster below to help describe JOIN types in SQL Server. This had lead to lots of confusion over time, and this is the best way that I have seen to describe them.
If you are looking for the MySQL version of the poster, click here.