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

Yes it's a complicated matter.

If you are still accepting feature requests for this, the 2 things that
Microsoft's solutions currently don't offer are:

1. Deferring the constraint evaluation to the end of the transaction
2. Evaluating the constraint on a statement/table-level and not for each
individual row

It would be great if you could include those.

2013/2/23 Fred Toussi <[email protected]>

>   It will support a wide range of subquries but not necessarily all
> possible subqueries, as a check condition must hold when referenced tables
> are modified.
>
>  Fred
>
>  On Sat, Feb 23, 2013, at 20:56, Timmy Turner wrote:
>
> > We will probably add some support in this area later this year.
>
>  Wow, this was unexpected. Can you provide any further details on what
> this might look like, or what amount of functionality you will be trying to
> cover?
>
>  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)
>
>  2013/2/23 Fred Toussi <[email protected]>
>
>    The documentation states the Standard and mentions any difference in
> implementation. In this case it misses the fact that subqueries are not yet
> supported in check constraints.
>
>  We will probably add some support in this area later this year.
>
>  Fred
>
>  On Sat, Feb 23, 2013, at 20:31, Timmy Turner wrote:
>
>  Hi,
>
>  on
> http://hsqldb.org/doc/2.0/guide/databaseobjects-chapt.html#dbc_constraints(or page 48 in the PDF) it says:
>
>  "A CHECK constraint consists of a <search condition> that must not be
> false (can be unknown) for each row of the table. The <search condition>can reference all the columns of the current row, and if it contains a
> <subquery>, other tables and views in the database (excluding its own
> table)."
>
>  Is this actually true or an error in the documentation? Trying a subquery
> in a check constraint gives me a FeatureNotSupportedException.
>
>  Are there any plans to support this functionality (or Assertions in
> general) in the near future?
>
>
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