Hi,

>I can't find a complete SQL reference for all statements and it's very
>hard to incrementally scan all the release notes, so I might have
>missed something.

The language reference updates may be more easy sometimes:
http://www.firebirdsql.org/refdocs/langrefupd20.html
http://www.firebirdsql.org/refdocs/langrefupd15.html


Although, release notes may be more complete.

>Given the fact that Firebird tries to be ANSI compliant as much as
>possible, it's hard to believe that deferred constraints are not
>supported (which are defined in SQL92 to my knowledge)

Well... they're not supported AFAIK. Firebird really tries to be ANSI
compliant for all features that it does implement. You may read more about
it here:

http://www.firebirdsql.org/index.php?op=devel&sub=engine&id=SQL_conformance



Regards,
Anderson Farias