Darren Duncan wrote:
> I think it would be best that the generic cast syntax only be useable
> for casts defined on the base type, and if you want a domain-specific
> one you should use the function syntax such as your datetime2int().
>
> That way it is easier for users to predict what behavior will occur, and
> implementation will be easier too.
Replying to myself, I offer another alternative:
What you ask for is indeed supported, but that if for a given input value more
than one cast applies to it, particularly for 2 overlapping domains, then which
cast is invoked is undefined, so for example the DBMS may just use the first one
it finds.
It is then up to the user to ensure that when they define casts over domains
that they just define ones that either produce the same outputs for the same
overlapping inputs (the best answer) or they ensure that they don't overlap in
their input domains.
-- Darren Duncan
