Re: E-R diagram code U1

Rich Shepard <rshepard@appl-ecosys.com> writes:
>    Looking at the entity-relationship diagram for a regulatory agency database
> they have attribute identifiers of PK, FKn, and U1. The first is the Primary
> Key and the second is a Foreign Key, but I've not before seen a 'Un'
> identifyier. I've no idea what DBMS they're using (but suspect Oracle). My
> web search used in-effective terms so I could not find the answer there.

>    What does U1 represent?

Unique constraint, perhaps?  I'm just guessing.

            regards, tom lane