Re: Unique constraints and indexes.

On 05/01/16 19:47, Tom Lane wrote:
> Steve Rogerson <steve.pg@yewtc.demon.co.uk> writes:
>> Is this a bug? I create a "unique" index, directly but it doesn't add a unique
>> constraint. Add a unique constraint and it adds the index and the constraint.
>
> That's operating as designed.  A unique constraint needs an index,
> but not vice versa.


I can see that might be plausible , hence the question but as a "unique index"
imposes as constraint they seem equivalent. What's the functional difference
between the two situations?

Steve