How many employed disabled students have zero absences?
employed students refers to disabled.name who are NOT in unemployed.name; zero absences refers to month = 0;
SELECT COUNT(T1.name) FROM longest_absense_from_school AS T1 INNER JOIN disabled AS T2 ON T1.name = T2.name INNER JOIN unemployed AS T3 ON T3.name = T2.name WHERE T1.month = 0