SQL Joins explained visually

A really good explanation of SQL joins. This is a major part of what I do at work. Well written SQL is a joy to behold and complex, obtuse SQL can cause physical pain. [Link]

Since SQL joins appear to be set-based, the use of Venn diagrams to explain them seems, at first blush, to be a natural fit. However, like the commenters to her post, I found that the Venn diagrams didn't quite match the SQL join syntax reality in my testing. I love the concept, though, so let's see if we can make it work.

For most purposes, it does work. The cases where is doesn't, well, it's close enough without being pedantic.