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
primarykey constraint that I define in a base table is not inherited. Are any constraints inherited? What happens if
Ideclare 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
thereis a more serious problem: how can I ensure that these keys are unique across all of the derived tables? (i.e. if
T1and 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
hasany value of (id,xx).)
Is this a possible area for future enhancements?
Regards,
--Phil.
