Løsningsforslag uke 9 INF212 - Våren 2002 Jørgen Hermanrud Fjeld with precious assistance from Marte Arnestad Harald Askestad Kai-

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1 Løsningsforslg uke 9 INF212 - Våren 2002 Jørgen Hermnrud Fjeld <jorgenhf@i.uio.no> with preious ssistne from Mrte Arnestd Hrld Askestd Ki-Roert Bjørnstd Tor Even Rmerg 8. mrs SELECT A B Mens B is lis of A, sine this is shorthnd for: SELECT A AS B To selet A nd B s different ttriutes, we would write: SELECT A, B SELECT MODEL, SPEED, HD WHERE PRICE < 1200; SELECT MODEL, SPEED AS MEGAHERTZ, HD AS GIGABYTES 1

2 WHERE PRICE < 1200; SELECT FROM WHERE mker Produt type LIKE 'printer'; d, rm, sreen FROM Lptop WHERE prie > 2000; e SELECT * FROM Printer WHERE olor ; f, speed, hd WHERE prie < 2000 AND (rd = '12xDVD' OR rd = '16xDVD' ) ; R NULL NULL NULL i i NULL i j i, j re ritrry integers, ut not NULL (,) is tuple of ttriutes nd. mens or: thus (i,j NULL) mens ll tuples where is ny integer i, nd is ny other integer j, or the vlue NULL. 2

3 = 10 OR = 20 (10,i NULL) (i NULL,20) = 10 AND = 20 (10,20) < 10 OR >= 10 (i,j NULL) d = (i,i) e <= (i,j) where i<=j SELECT * FROM Movie WHERE length <= 120 OR length > 120 ; Simpler nd equivlent: SELECT * FROM Movie WHERE length IS NOT NULL; 3

4 6.2.2 SELECT P.mker, L.speed FROM Produt AS P, Lptop AS L WHERE L.hd >= 30 AND P.model = L.model ; ( SELECT P.model AS model, C.prie AS prie FROM Produt AS P, PC s C WHERE mker = B AND P.model = C.model ) UNION ( SELECT P.model AS model, C.prie AS prie FROM Produt AS P, Lptop s C WHERE mker = B AND P.model = C.model ) UNION ( SELECT P.model AS model, C.prie AS prie FROM Produt AS P, Printer s C WHERE mker = B AND P.model = C.model ) ( SELECT mker FROM Produt WHERE type = 'lptop' ) EXCEPT ( SELECT mker FROM Produt WHERE type = 'p' ) d SELECT PC.hd AS PC, PC AS PC' WHERE PC.hd = PC'.hd AND PC.model <> PC'.model ; e SELECT PC.model, PC'.model 4

5 AS PC, PC AS PC' WHERE PC.speed = PC'.speed AND PC.rm = PC'.rm AND PC.model > PC'.model ; f -- Get those who hve two different PC models ( SELECT P1.mker FROM Produt AS P1, Produt s P2, PC AS C1, PC s C2 WHERE C1.speed >= 1000 AND C2.speed >= 1000 AND P1.model = C1.model AND P2.model = C2.model AND C1.model <> C2.model AND P1.mker = P2.mker ) UNION -- Get those who hve two different Lptop models ( SELECT P1.mker FROM Produt AS P1, Produt s P2, Lptop AS C1, Lptop s C2 WHERE C1.speed >= 1000 AND C2.speed >= 1000 AND P1.model = C1.model AND P2.model = C2.model AND C1.model <> C2.model AND P1.mker = P2.mker ) UNION -- Get those who hve different Lptop nd PC model ( SELECT P1.mker FROM Produt AS P1, Produt s P2, PC AS C1, Lptop s C2 WHERE C1.speed >= 1000 AND C2.speed >= 1000 AND P1.model = C1.model AND P2.model = C2.model AND C1.model <> C2.model AND P1.mker = P2.mker ) 5

6 6.3.1 SELECT mker FROM Produt WHERE model IN ( WHERE speed >= 1200 ); SELECT mker FROM Produt WHERE model = ANY ( WHERE speed < 1200 ); SELECT mker FROM Produt AS P WHERE EXISTS ( SELECT * WHERE PC.model = P.model AND speed >=1200 ) ; FROM Printers WHERE prie >= ALL ( SELECT prie FROM Printers ) ; FROM Printers WHERE NOT prie < ANY ( SELECT prie FROM Printers ) ; FROM Lptop WHERE speed < ALL ( SELECT speed ); 6

7 FROM Lptop WHERE NOT speed >= ANY ( SELECT speed ); d FROM ( (, prie ) UNION (, prie FROM Lptop ) UNION (,prie FROM Printers) ) AS C WHERE C.prie >= ALL ( ( SELECT prie ) UNION ( SELECT prie FROM Lptop ) UNION ( SELECT prie FROM Printers) ) ; FROM ( (, prie ) UNION (, prie FROM Lptop ) UNION (,prie FROM Printers) ) AS C WHERE NOT C.prie < ANY ( ( SELECT prie ) UNION ( SELECT prie FROM Lptop ) UNION ( SELECT prie FROM Printers) ) ; e SELECT mker FROM Produt AS P, Printer s C WHERE C.olor AND P.model = C.model AND C.prie <= ALL ( SELECT prie FROM Printer WHERE olor ) ; SELECT mker FROM Produt AS P, Printer s C WHERE C.olor AND P.model = C.model AND NOT C.prie > ANY ( SELECT prie FROM Printer WHERE olor ) ; 7

8 f SELECT mker FROM ( SELECT * WHERE rm <= ALL (SELECT rm ) ) AS PC', Produt s P WHERE P.model = PC'.model AND speed >= ALL ( SELECT speed WHERE rm <= ALL (SELECT rm ) ) ; SELECT mker, Produt WHERE.model =.model AND speed >= ALL ( SELECT speed WHERE.rm = PC.rm AND PC.rm <= ALL ( SELECT rm ) ); R CROSS JOIN S; -- n e written s SELECT * FROM R, S ; R NATURAL JOIN S; This n't e written out without knowing the ommon ttriutes. It would e something like: SELECT R.pttr1,..., R.pttrM, S.pttr1,..., S.pttrN, R.ttr1 s ttr1,..., R.ttrJ s ttrj FROM R, S 8

9 WHERE R.ttr1=S.ttr2 AND R.ttr2=S.ttr2 AND... R.ttrJ=S.ttrJ; Give R nd S where <pttrx> is n ttriutenme not shred y the reltions, nd <ttry> is n ttriutenme shred y the reltions. R JOIN S ON C ; -- n e written s SELECT * FROM R, S WHERE C ; -- C is ondition SELECT AVG(speed) AS menspeed ; SELECT AVG(speed) AS menspeed FROM Lptop WHERE prie > 2000 ; SELECT AVG(prie) AS menprie FROM Produt s P, PC WHERE P.model = PC.model AND P.mker LIKE 'A' ; 9

10 d SELECT AVG(prie) AS menprie FROM ( (,prie ) UNION (,prie FROM Lptop) ) AS C, Produt AS P WHERE P.model = C.model AND P.mker = 'D' ; e SELECT speed, AVG(prie) AS menprie GROUP BY speed; f SELECT mker, AVG(sreen) FROM Produt AS P, Lptop s C WHERE P.model = C.model GROUP BY mker; g SELECT mker FROM Produt WHERE type = 'PC' GROUP BY mker HAVING COUNT(*) >= 3; -- Siden COUNT(*) utføres for hver enkelt gruppe v mker h SELECT mker, MAX(prie) AS mxprie FROM Produt s P, PC WHERE P.model = PC.model GROUP BY mker; i SELECT speed, AVG(prie) AS menprie 10

11 WHERE speed > 800 GROUP BY speed; j SELECT mker, AVG(hd) AS menhd, Produt p WHERE.model = p.model AND mker IN ( SELECT mker FROM Produt WHERE type = 'Printer' ) GROUP BY mker; 11