[SQL] Oracle subquery in join statement

In Oracle, it's possible to use sub queries in a join statement by giving an alias to the subquery and joining on that alias:

SELECT a.column1, a.column2, c.column3

FROM a JOIN (

SELECT b.column1, b.column2, b.column3

FROM b

) c

ON (a.column1 = c.column1 AND a.column2 = c.column2)

Obviously you would never write a SIMPLE query EXACTLY as the example above, it's just to show the mechanics when you actually need to create a slightly more complex one