select *
from people
where id not in
(
select id
from class_registration
)
In my experience, queries like the OUTER LEFT JOIN version posted
earlier are usually much more efficient than NOT IN queries like the
above. The planner seems to be pretty smart about turning (positive)
IN queries into joins, but NOT IN queries usually turn into nested
table scans, in my experience.
- John D. Burger
MITRE
---------------------------(end of broadcast)---------------------------
TIP 3: Have you checked our extensive FAQ?
http://www.postgresql.org/docs/faq
