yikes

delimiter $$
create trigger HELLO_CUSTOM_FIELD_INSERT_TRIGGER after insert on HELLO_CUSTOM_FIELD for each row
begin
        declare l_count int default 0;
        select count(*)
        from HELLO_CUSTOM_FIELD hcf
        where
                hcf.owner_uri_path_id = new.owner_uri_path_id and
                hcf.owner_uri_ref = new.owner_uri_ref and
                hcf.namespace_prefix = new.namespace_prefix and
                hcf.namespace_prefix <> '' and
                hcf.namespace <> new.namespace and
                hcf.id <> new.id
        into l_count;

        if l_count > 0 then
                insert into ERROR (message) values ('Namespace prefix cannot be shared by multiple namespaces');
        end if;

        select count(*)
        from HELLO_CUSTOM_FIELD hcf
        where
                hcf.owner_uri_path_id = new.owner_uri_path_id and
                hcf.owner_uri_ref = new.owner_uri_ref
        into l_count;

        if l_count > 100 then
                insert into ERROR (message) values ('Each account is limited to 100 custom fields for each object type');
        end if;
end;
$$
delimiter ;