A have several tables I would like to be able to loosely associate
properties. For simplicity lets say they are VARCHAR properties and
that the user can define various types. The string_property table
might look like this:

REF_ID NUMERIC // F_KEY
TYPE_ID NUMERIC
VALUE VARCHAR
Primary Key { REF_ID, TYPE_ID }

A Property Type might be something like "COLOR" which has a default
value of "Orange".

So this is pretty simple. This string_property table has a row for
each ID of the rows in the table it is being associated with. We'll
call this the Subject table. For simplicity lets just say that every
Subject row can have just one string_property row associated with it
for any given TYPE.

The problem is that there could be millions of rows in the Subject
table and only some of them might have a COLOR property other than the
default of Orange. I don't want to create a row in the string_property
table for each Subject with the COLOR of Orange.

So the question is this. How do I query for Subjects that have a
Property that matches some arbitrary condition. The condition may or
may not match the default property value.

What I have come up with is pretty ugly, is there a better solution?

My solution assumes that for every TYPE_ID there will be just one row
written with the default value and whose REF_ID is a well-known ID
that cannot exists in any Subject table. Let's assume this ID is 0.

The query then looks something like this:

SELECT *
FROM Subject
WHERE
(
(Subject.ID NOT IN (SELECT * FROM SPROP))
AND
((SELECT REF_ID FROM SPROP WHERE VALUE LIKE "Orange") == 0)
)
OR
(
Subject.ID IN (SELECT * FROM SPROP WHERE VALUE LIKE "Orange")
);

The syntax may not be exactly correct, but would that be the correct
logic? Is there another way I should be doing this (short of writing a
record for each default that a Subject row implicitly has)?

TIA