Hi Helen,

>>> constraint un_tags_name unique(name)
>> In a multi-user environment I'll have to be prepared for this
>> to fail (two users added the same new tag at the same time).
>
> Ummm, fail? The tag only has to be entered once. If it's there
> already, it doesn't need to be added: an exception will take care
> of it.

Two separate transactions, second fails on commit, then need to retry.
There's at least a small window where select existing tag finds nothing and
commit of first before commit of second causes second to fail.

Regards,

Jarrod Hollingworth
Complete Time Tracking
http://www.complete-time-tracking.com/