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Date: Fri, 29 Nov 2002 22:50:27 -0500
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From: "A.M." <agentm@cmu.edu>
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I have a reference which is guaranteed not to have a valid reference 
(preferably NULL) until it is processed later. How can I defer a 
reference entry so that both NULL and an actual reference are valid in 
the reference field? The processing which I speak of takes place later 
and not in the same transaction (thus making DEFERRABLE useless, 
right?). A solution I thought of is to forget keys and just make it an 
INT8 since I am also guaranteed that its referenced item is never 
deleted. But certainly, there is a more reliable way to do it, right?
	In summary, what I want is

  field INT8 REFERENCES sometable NULL OK

or

field INT8 CHECK(SELECT id FROM someothertable WHERE field=id)

(can I do this? this allows NULL right?)

The rule is ref2 can either be a valid reference or NULL.
CREATE TABLE thetable(
	ref2 INT8 REFERENCES someothertable,
	...
);

Thanks for any help.
 ><><><><><><><><><
AgentM
agentm@cmu.edu