Actually, I’ve always been a bit shaky on joins myself. I always have to look them up any time I need to using a join that isn’t a standard filtered cross product. But seeing this visual guide has really helped me to grasp it much better. I just went back and read the Wikipedia entry for joins and it makes complete sense to me now. Before seeing this visual representation I might have just glazed over when reading the Wikipedia article.
So even if they aren’t exactly right having a visual representation has really helped me to understand what is going on.
Thanks!