OK so I revised it to this.
SELECT DISTINCT TEST.sample_id, NANDAT.art, maxi, summe
FROM TEST, NANDAT
WHERE art Not In(66,88,90,95,94,131,132,133)
AND TEST.sample_id=NANDAT.sample_id
AND TEST.maxi=NANDAT.data
GROUP BY TEST.sample_id, NANDAT.art, maxi, summe;
This worked except that where...