I asked if derived tables use primary key indexes generated in the base tables that
they inherit from.
Franco Bruno Borghesi replied:
> [the derived table] is not inheriting any indexes, neither the
> primary key constraint.
OK, thanks! I had come to the conclusion that it was not using the index, but I'm
really surprised to hear that the primary key constraint that I define in a base table
is not inherited. Are any constraints inherited? What happens if I declare a
single-column primary key? What if I declare a "not null" constraint or a "check"
constraint in a base table?
Having to replicate the constraints and indexes for each derived table is a pain -
lots of error-prone typing - but there is a more serious problem: how can I ensure
that these keys are unique across all of the derived tables? (i.e. if T1 and T2
inherit from B, and B's primary key is (id,xx), then I want there to be at most one
row in (T1 union T2) that has any value of (id,xx).)
Is this a possible area for future enhancements?
Regards,
--Phil.
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