From: | Ben Clewett <B(dot)Clewett(at)roadrunner(dot)uk(dot)com> |
---|---|
To: | |
Cc: | pgsql-novice(at)postgresql(dot)org |
Subject: | 'UNIQUE' |
Date: | 2003-03-17 14:33:41 |
Message-ID: | 3E75DCC5.9040208@roadrunner.uk.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-novice |
Hi,
To describe an optional 1:1 reference I am using the 'UNIQUE' keyword:
key_foo INT UNIQUE,
FOREIGN KEY (key_foo) REFERENCES ....
Does 'UNIQUE' allow multiple 'NULL' entries?
Ie:
key_foo
-------
1
2
NULL
9
8
NULL
4
NULL
If as I expect, this is not the case, could anybody recommend another
way of forming an optional 1:1 reference?
--------x-------X-------x--------
I have a problem of 'stale' data. I want to produce combo-box's of
selectable options, which are PK's of a table. In order to enhance the
system, I want to be lazy and store the values in the control. To do
this I need some way of telling when the source table / view is out of
date and the data has changed.
I could set up Triggers to amend some lookup table containing a
timestamp of the change for a table. But I am wondering if PostgreSQL
stores the last write timestamp to a table somewhere where it can be
checked easily?
Thanks again,
Ben Clewett.
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2003-03-17 14:51:45 | Re: 'UNIQUE' |
Previous Message | David Haines | 2003-03-17 02:43:11 | Postmaster.pid & Unix domain socket errors, OS X |