August 2nd, 2011, 01:14 PM
Differances between INNER JOIN and OUTER JOIN
I was curious as to the situations when you would use INNER JOIN over OUTER JOIN and OUTER JOIN over INNER JOIN and what data LEFT JOIN would pull? I am currently using INNER JOIN to join 2 tables for relational reasons but cant really figure out OUTER JOIN so thought I should ask.
August 2nd, 2011, 01:47 PM
August 2nd, 2011, 02:23 PM
August 2nd, 2011, 04:47 PM
So the full outer join is saying everything that doesn't match from table a and table b as in your example?
August 2nd, 2011, 04:49 PM
oh, that would only be the case if we did a where clause for NULL?
August 2nd, 2011, 05:12 PM
yeah, sort of
Originally Posted by reaper7861
see, the diagrams are also hard to grasp at first, aren't they
also, notice there is no diagram for cross join
August 2nd, 2011, 06:15 PM
Yes i noticed that and didn't even know that cross joining existed, I am curious as to what you would use that for?
August 2nd, 2011, 06:46 PM
you would use a cross join to generate all possible combinations of pairs of values
just remember that, and you will recognize the opportunity when it arises -- which isn't often, admittedly, but the cross join can be very useful
August 2nd, 2011, 06:54 PM
That is great information, thanks a lot.