Helen Borrie wrote:

>>Yes it does. Try local="ab", host="c" vs. local="a", host="bc". The
>>second will be incorrectly rejected by the UNIQUE(local,host) constraint
>>but correctly accepted by UNIQUE(local,ampersand,host).
>
> No, you are mistaken. The index does *not* get concatenated: it stays as
> two distinct columns. So you will have:
>
> Local Host
> ab c (a unique combination)
> a bc (another unique combination)

Oops, you're right. I don't know why I thought it gets concatenated
before. Of course it does not. Thanks for reminding me.

--
dave