Skulle något liknande fungera?
SELECT
max(a.field_date_and_time_value2) as last_time
, b.uid
FROM field_data_field_date_and_time a
INNER JOIN
node b
ON
/* this piece might be wrong. what is the relationship between the first table and the second one? */
b.nid = '".$node->nid."'
where
a.field_date_and_time_value2 > '".$today."' AND
b.uid = $node->nid