My first gut reaction was that this code is broken and would not run. To my amazement code ran just fine. Now came the hard part, which was to figure out what the code was doing because I have never seen this syntax before. Since I did not understand what I was looking at I could not BING “weird join syntax” to get an answer. As a developer, I learned long time ago to break down code into smallest possible chunks to get the answer.
After I have figured out the relationship between tables, I was able to understand what query was doing. To be able to read query better it can be rewritten in the following way.
Do read Vlad’s post. I’ve seen terrible misuse of this plus right outer joins, and I don’t know if I’ve ever seen a case where using this syntax made the code easier to understand.