Oracle Database Discussions

Hi Guys,
A mate asked me about the different join types and their were a few I was really uncertain about. I did some research and came up with the definitions below but those do not clearly differentiate the four (especially Cross Join and UNION).

Difference between:

1. Full Outer join
"set of all combinations of tuples in R and S that are equal on their common attribute names"

2. Cross Join = Cartesian Product
"A cartesian join is a join of every row of one table to every row of another table"

3. Natural Join
"A natural join is a join statement that compares the common columns of both tables with each other. "

4. Union
"set operation that returns all rows from two different select statements, and then eliminates any duplicate rows from the result set. "