SELECT a.articleName,
a.articleUnit,
p.articlePrice,
s.SupplierName
FROM tblArticle as a
INNER JOIN tblPrice as p ON a.articlenumber = p.articleNumber
INNER JOIN tblSupplier as s ON p.articleSupplierId = s.SupplierId
WHERE tblArticle.articleName = Kabel
and articlePrice in
(select max(price)
from articleprice as ap
where p.articelNumber= ap.articleNumber)
union all
SELECT a.articleName,
a.articleUnit,
p.articlePrice,
s.SupplierName
FROM tblArticle as a
INNER JOIN tblPrice as p ON a.articlenumber = p.articleNumber
INNER JOIN tblSupplier as s ON p.articleSupplierId = s.SupplierId
WHERE tblArticle.articleName = Kabel
and articlePrice in
(select min(price)
from articleprice as ap
where p.articelNumber= ap.articleNumber)
order by a.articleName