SELECT *
FROM Lecturer
WHERE id NOT IN
    (
    SELECT DISTINCT lect_id
    FROM Var_Assignment
    )

SELECT sf.id, sf.name, count(lect.id)
FROM Sub_Faculty sf LEFT JOIN Lecturer lect ON sf.id = lect.sub_fact_id
WHERE lect.id NOT IN
    (
    SELECT DISTINCT lect_id
    FROM Var_Assignment
    )
GROUP BY sf.id, sf.name