A correlated subquery that appears in an aggregate value inside of a subquery, will not have the correlated values available and fail with a TEIID30328 exception.

For example:

SELECT g0.a, g0.b, (SELECT max((SELECT g2.a FROM m.z AS g2 WHERE g2.b = g1.a)) FROM m.y AS g1 WHERE g0.a = g1.b) FROM m.x AS g0

will fail on the g0.a reference.