NikhilS <nikkhils(at)gmail(dot)com> writes:
> I just now realized that even though we allow the above. We do not allow:
> pg=# create table t1 (a int, b int, unique(a+b));
> Any specific reason for this behaviour?
It'd be contrary to SQL spec. The UNIQUE constraint takes a list of
column names, full stop.
regards, tom lane