Re: [SQL] Meta integrity

[Tom Lane]

Renato De Giovanni <[EMAIL PROTECTED]> writes:
>        FOREIGN KEY (object_id, 'X') REFERENCES object (id, class_id)

Why not just store the class_id in the secondary table (if you're
concerned about space, consider using an int4 to represent class_id).
Then you can do a direct two-column foreign key constraint, plus add
a check constraint like CHECK(class_id = 'X').

                        regards, tom lane

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