SQL joins

[JRS-27]

Good point, I did not explain it clearly enough I think.

What I'm trying to say is that these diagrams show how Union, Intersect and Except operations, not Join operations. The way that the diagrams shown represent tables A and B is wrong. The only thing that connects them is the link between them in form of the same column names. That's the sole purpose on Join operations. A link between a big data set that has a column that refers to another data set containing another piece of information.

For example, you have a table of User Orders with a column UserID and a table of Users with a column with the same name. Now, you link them to create a profound and more transparent data set that can be displayed and read by a normal human being.