Re: Error in Documentation? (Subqueries in CHECK Constraints / SQL92-Assertions)

A check constraint conforming to SQL Standard is not any arbitrary
constraint that you can hide in a function.

If must be "retrospectively deterministic", which means deterministic at
any future time. For example, HSQLDB supports CHECK (COL <
CURRENT_DATE), but rejects CHECK (COL > CURRENT_DATE). There are very
strict rules on what is allowed and HSQLDB supports a subset of
allowable check constraints.

Fred

On Mon, Feb 25, 2013, at 8:29, Thomas Kellerer wrote:
> Timmy Turner, 23.02.2013 21:56:
> > That would add HSQLDB to the list of currently only 2 SQL-based
> > DBMSes that somewhat support this (one being MS Access/JET(1) and the
> > other MS SQLServer(2)).
> >
> > (1) http://support.microsoft.com/kb/201888/en-us
> >
> > (2)
> > http://sqlblog.com/blogs/alexander_kuznetsov/archive/2009/06/25/scalar-udfs-wrapped-in-check-constraints-are-very-slow-and-may-fail-for-multirow-updates.aspx
> >
> > Found those links on http://stackoverflow.com/questions/6368349/why-dont-dbmss-support-assertion
> >
> 
> If you are willing to "hide" the check behind a stored function, then the
> list is a bit longer than just MS Access and SQL Server.
> At least in Postgres and Oracle you can do the same thing.
> 
> Thomas
> 
> 
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