>
>
>Hi Dani,
>
>I understand that part :)
>
>but what about the extra options you can specify in the join
>condition, like 'outer' , 'inner', 'full' etc
>
>i dont see a circumstance when you would use the extra options...
>
>
Hi,
these options are useful when your tables are partially related.
For example, you have a table products and a table color.
Now some products don't have a color (like a computer Program).
If you would state this join:
Select product.name, color.name
from
product,
color
where product.color_id = color.color_id (This is an INNER Join, by the Way)
You would NOT retreive the products whose
color_id is NULL.
Thats where the OUTER JOIN comes in - but this is - as far as i know-
not directly supported in Postgres.
You have to do this:
Select product.name, color.name
from
product,
color
where product.color_id = color.color_id
UNION
Select product.name, 'No color'
from
product
where
color_id IS NULL;
You find a nice introduction on all this here:
http://spot.colorado.edu/~marangak/main.html
(But they speak about Oracle, not Postgresql)
I hope this gives you some clues.
Cheers, Dani
