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