Giovanni Campagna wrote:
We have a standard SQL, and we have DBMS-specific extensions (for
SQLite, for MySQL, for SQLServer, etc.).
> The latest version is "ISO/IEC 9075:2008 Information technology --
> Database languages -- SQL", released in 2008, but actively being
> revised, according to the ISO page.
Sort of. "Extensions" implies that as long as you write a query to the
ISO standard in question the behavior will be the same in all databases
and that you have to go out of your way to write non-interoperable
queries. This is not the case. A query written based on that ISO
standard has different behavior in different databases, in many cases.
So just telling web authors "write queries based on this standard and
they will work" is not sufficient. Let's ignore the fact that most web
authors wouldn't be able to even get their hands on this standard to see
whether their query complies with it without paying a fairly hefty sum [1].
You could also require UAs to implement queries exactly per this
standard. Vladimir mentioned as a possible option in his original post.
This is definitely the way forward (with either this SQL definition or
some subset thereof)
As usual, if you want interoperability, you use the existing,
implemented, standard (or you ask the ISO to produce an updated
standard with new features), else you use extensions.
Use of the existing standard by authors doesn't give interoperability.
-Boris
[1]
http://www.iso.org/iso/search.htm?qt=9075&searchSubmit=Search&sort=rel&type=simple&published=on
tells me that to get just the parts of ISO 9075:2008 that are obviously
necessary to be able to do anything whatsoever will cost me either about
$290 or $770 depending on what's in part 2 of the spec. I'm assuming
none of parts 3,4,9,10,11,13,14 are relevant to our use case; this is
probably a good assumption for most of them. That's for getting a PDF,
of course; the PDF on CD prices are somewhat higher, and there seem to
be no other provisions for looking at this specification.
