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05-26-2006, 04:32 AM
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Oracle dialect question:
How do I avoid chicken and egg problems?Say If I have a table which defines a foreign key constraint on another table which itself does not yet exist? I cant create such a table as I keep getting an exception
    
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05-26-2006, 04:37 AM
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Oracle answer.
Re: How do I avoid chicken and egg problems?
You can use deferrable constraint checking in this scenario
Code:
CREATE TABLE chicken(chickenID INT PRIMARY KEY, eggID INT);
CREATE TABLE egg(eggID INT PRIMARY KEY, chickenID INT);
Then, we add foreign key constraints:
ALTER TABLE chicken ADD CONSTRAINT chicken_gg
FOREIGN KEY (eggID) REFERENCES egg(eggID)
INITIALLY DEFERRED DEFERRABLE;
ALTER TABLE egg ADD CONSTRAINT egg_chicken
FOREIGN KEY (chickenID) REFERENCES chicken(chickenID)
INITIALLY DEFERRED DEFERRABLE;
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