A visualisation of SQL Joins
Generally speaking, every result set that is created by a join is a certain combination of rows which are stored in MySQL tables. Even if you join more than two tables, MySQL always combines two result sets at a time. These result sets can be visualized with the help of so called Venn Diagramms, a mathematical representation of sets. Taking a look at them sometimes makes it easier to understand what’s actually happening. In addition, the human brain can store information like the different MySQL join operations or the related MySQL join syntax if it can connect them with some kind of picture. That’s the reason why we provide a graphical representation (a Venn Diagramm) for every MySQL join tutorial. You can access them by browsing all available “join tutorials“.
In addition, the following pages provides an overview which is very interesting as well. It combines all the different possible result sets in just one graphic: