Ao usar NOT IN, você deve garantir que nenhum dos valores seja NULL:
SELECT mac, creation_date
FROM logs
WHERE logs_type_id=11
AND mac NOT IN (
SELECT mac
FROM consols
WHERE mac IS NOT NULL -- add this
)
SELECT mac, creation_date
FROM logs
WHERE logs_type_id=11
AND mac NOT IN (
SELECT mac
FROM consols
WHERE mac IS NOT NULL -- add this
)
