Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> create table constants (type text, id int primary key, value text);
> create unique index x_const_idx on constants(id) where type = 'x';
> create table client (id serial primary key; xid int references
> constants(id) using x_const_idx);
This seems like a solution in search of a problem. Why wouldn't you
just use separate reference tables? Adding such a concept would break
more things than I even want to think about (information_schema for
starters).
regards, tom lane