Hi John,

> Can a check constraint see other records? I thought they could only
> see the fields in the current record?

There are two types of CHECK constraints --

1) column check constraints
eg: MYVAL INTEGER CHECK (MYVAL > 1)

2) table check constraints
Can operate on multiple columns
(MYVAL > 1 AND MYCOL = 0)

or can have complex SELECTs etc etc...

With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server.
Upscene Productions
http://www.upscene.com

> --- In firebird-support@yahoogroups.com, "Martijn Tonies"
> <m.tonies@u...> wrote:
> > Hi John,
> >
> >
> > > You don't *need* to use a trigger, but using your solution has
> the
> > > same problem - if there is an uncommitted record in another
> > > transaction (with an overlapping time-period), you won't see it,
> and
> > > it won't see you.
> > >
> > > You'll both commit fine. And then you've got a problem.
> >
> > How about using a CHECK constraint? Doesn't that solve
> > your problem?
> >
> > With regards,
> >
> > Martijn Tonies
> > Database Workbench - developer tool for InterBase, Firebird, MySQL
> & MS SQL
> > Server.
> > Upscene Productions
> > http://www.upscene.com
>
>
>
>
>
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