Re: outer join between parent-child, not null and FK constraints
From: amonte <ax.mount_at_gmail.com>
Date: Fri, 25 Jan 2013 08:02:26 +0100
Message-ID: <CABV7K9vMQH1OXXfcT3b0diAKScC1feggfbEN5CkV0dX4eby8sQ_at_mail.gmail.com>
Hi David
As you say outer join returns all values from one table even there are no matches.
Date: Fri, 25 Jan 2013 08:02:26 +0100
Message-ID: <CABV7K9vMQH1OXXfcT3b0diAKScC1feggfbEN5CkV0dX4eby8sQ_at_mail.gmail.com>
Hi David
As you say outer join returns all values from one table even there are no matches.
In a parent child relation ship all child must have a parent (unless the child tabla rows has a null for FK). If the FK is enforced a NOT NULL then the child table must have a value pointing to a parent correct? What I am saying is that if we have FK plus NOT NULL then all child must have a match in parent table so outer join with parent table is redundant because there is no way a child table wont match a parent row.
Unless I am missing some situation that even with FK and NOT NULL there wont be matches between child and parent?
Alex
-- http://www.freelists.org/webpage/oracle-lReceived on Fri Jan 25 2013 - 08:02:26 CET