--6
SELECT cisdod FROM Dodava
WHERE cissou=15 AND cisdod IN(
	SELECT cisdod FROM Dodava Where cisdod<>15)
EXCEPT
--6
SELECT DISTINCT cisdod FROM Dodava
WHERE cisdod IN(
SELECT cisdod FROM Dodava WHERE cissou=15
)AND cissou<>15

--7
SELECT cisdod FROM DOdava WHERE cissou=15
EXCEPT
SELECT cisdod FROM Dodava WHERE cissou<>15
--7
SELECT cisdod FROM Dodava WHERE cissou =15 AND cisdod NOT IN(
	SELECT cisdod FROM Dodava WHERE cissou <>15
)
--7
SELECT X.cisdod FROM Dodava X
Where X.cissou = 15
	AND NOT EXISTS(
		SELECT Y.cisdod FROM Dodava Y
		WHERE cisdod = Y.cisdod
			AND Y.cissou <> 15
	)


--8
SELECT DISTINCT cisdod FROM Dodava WHERE cissou<>15
AND cisdod NOT IN (
	SELECT cisdod FROM Dodava WHERE cissou =15
)

--9
SELECT cisdod FROM Dodava WHERE cissou =12
INTERSECT
SELECT cisdod FROM Dodava WHERE cissou =13
INTERSECT
SELECT cisdod FROM Dodava WHERE cissou =15

--9
SELECT DISTINCT cisdod FROM Dodava D
WHERE (12) IN (
	SELECT cissou FROM Dodava E Where D.cisdod=E.cisdod
)AND (13) IN (
	SELECT cissou FROM Dodava E Where D.cisdod=E.cisdod
)AND (15) IN (
	SELECT cissou FROM Dodava E Where D.cisdod=E.cisdod
)

--10
SELECT cisdod FROM Dodava
EXCEPT
SELECT cissou FROM
(
	SELECT DICTINCT A.cisdod, B.cissou
	FROM Dodava A CROSS JOIN Dodava B
	EXCEPT
	SELECT cisdod FROM Dodava
)AS X


--11
SELECT DISTINCT mesto FROM Dodavatel, Dodava, Soucastka
WHERE Dodavatel.cisdod=Dodava.cisdod
AND Dodava.cissou=Soucastka.cissou
AND barva='cervena'

--12
SELECT avg(cena) AS 'Průměrná cena' FROM Soucastka