Would the set analogy hold if the "parts" where first all "promoted" to the ssame type via cross join, then filtered down, and finally joined? (I'm not sure if

Would the set analogy hold if the "parts" where first all "promoted" to the ssame type via cross join, then filtered down, and finally joined? (I'm not sure if this would make sense in general for sql, but it just occurred to me in terms of the type/category of sets involved in a join.. )