Checking number of entries

Hello,

Is it possible to restrict the number of entries in a table? I have attempted
to write a check like so:

    CREATE TABLE mytable (
        id integer NOT NULL,
        CHECK (COUNT(id) <= 10)
    );

This is not allowed, I get an error saying:

    ERROR:  ExecEvalAggref: no aggregates in this expression context

What is the proper way of doing this? I want to be able to force a minimum and
maximum number of entries.

Wade Oberpriller
StorageTek
oberpwd@network.com