CG <cgg...@yahoo.com> writes:
> For some of the referential constraints listed in my
> information_schema.referential_constraints table the values for the fields
> unique_constraint_catalog, unique_constraint_schema, and
> unique_constraint_name are NULL. There doesn't seem to be any rhyme or reason
> to which ones have values and which ones don't. They should all have values,
> right? Any ideas what could be going on?
PG will allow a foreign key constraint to be constructed when there is a
unique index for the referenced column(s). The unique index could have
been constructed via a UNIQUE or PRIMARY KEY constraint, or via a plain
old CREATE UNIQUE INDEX command. In the latter case there is no
constraint for the information_schema to show.
regards, tom lane
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