This would be without using THE to access a table (the table type being
accessed here is lines2, and you are accessing the end1 and end2 pointers
inside that table):
SELECT ll.end1.x, ll.end2.x
FROM Lines2 ll;
This would be with using THE to access a table:
SELECT ss.x
FROM THE(SELECT points
FROM Polygons
WHERE name = 'square'
) ss
WHERE ss.x = ss.y;
Question:
How do I know when a set of FD's is minimal? Is there a short cut?
Answer:
There really is no short cut. In order to decide that a set of FDs is
minimal you need to
1) Try to delete an FD.
2) Try to delete elements from the left side of an FD.
If these 2 steps fail (i.e., you cannot preform one of these steps and still
end up with an equivalent set of FDs), then you know you have a minimal
set. If not, then
you don't -- you can delete something from the set and start all over
again. It's a brute force algorithm. However, just like there were
certain techniques to determine which attributes were in keys to help speed
up the process of finding a minimal key, you can apply similar techniques
here to figure out which FD's you definitely cannot delete...