On Tuesday 11 January 2005 17:45, KÖPFERL Robert wrote:
> Hi,
>
> with what constraint or how can I ensure that one of my tables has exact
> one record or 0..1 records?
A trigger procedure BEFORE INSERT would help you.
And a column type with only one possible field value would help you if you
define UNIQUE INDEX on a field of this (user-defined) type.