Yes, I know there are differences, but what they are specifically, I'm not
sure.
I mention both since they are in the releaseNote :

(1.5) NULLs in unique constraints and indices
Dmitry Yemanov
.
---
Can a Unique constraints rely on a non unique index, or on no indices at
all ? As you can see, I don't know what's
going on in the engine regarding unique constraints / unique indices. But,
from an Application POV I can't really see any differences. Please set me
strait if I'm wrong here.

Anyway I think it would be nice if the change could apply to both.

> Hi,
>
>> Feature request: Changes in Unique constraint / Unique Index
>
> You do know that an Unique Index is something totally
> different from an Unique Constraint, right?
>
>> From the manual:
>>
>> The constraint allows existence of only those rows for which the
>> aforementioned <search condition>
>> evaluates to True. In a unique index or under a UNIQUE constraint, two
>> sets of column values will be
>> considered distinct and thus allowed if:
>> a) both sets contain only nulls, or
>> b) there is at least one pair of corresponding values of which one is
>> non-null, and the other either null
>> or a different non-null value.
>> .
>> .
>> .
>>
>> What I would like is that two or more sets of column values will be
>> considered distinct and thus allowed if: at least one contains nulls.
>>
>> After all isn't it safe to say that (1,null) is distinct from (1,null)
>> as
>> long as null is distinct from null ?
>
> With regards,
>
> Martijn Tonies
> Database Workbench - developer tool for InterBase, Firebird, MySQL & MS
> SQL
> Server.
> Upscene Productions
> http://www.upscene.com
>
>
>
>
> Yahoo! Groups Links
>
>
>
>

--
Trond.