摘要:●在下面的主程序中,实参a与形参x以引用调用(callbyreference)的方式传递信息,实参b与形参y以值调用(callbyvalue)的方式传递信息,那么,从过程"compute"返回主程序后a和b的值分别为___(16)___。MainprogramProcedurecompute(x,y)a:=1;b:=2;compute(a,b);x:=x+2*y;y
●在下面的主程序中,实参a与形参x以引用调用(call by reference)的方式传递信息,实参b与形参y以值调用(call by value)的方式传递信息,那么,从过程"compute"返回主程序后a和b的值分别为___(16)___。
Main program |
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Procedure compute(x,y) |
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a:=1; b:=2; compute(a,b); |
x := x + 2*y; y := 2*x + y; return; |
||
(16) A.5和2 B.5和12
C.l和2 D.1和12
●假设供应商S和供应情况SPJ的关系模式分别为:S(Sno,Sname,Status,City)和SPJ(Sno,Pno,Jno,Qty)。SQL语句__(17)___不能正确地查询出“零件号Pno等于‘P3’的供应商名Sname”,而__(18)___能正确查询的关系代数表达式。 [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
(17) A.SELECT DISTINCT Sname B.SELECT DISTINCT Sname
FROM S FROM S
WHERE EXISTSWHERERE 0<
(SELECT * (SELECT COUNT(*)
FROM SPJ FROM SPJ
WHERE S.Sno=SPJ.Sno WHERE S.Sno=SPJ.Sno
AND SPJ.Pno=’P3’) AND SPJ.Pno=’P3’)
C.SELECT SnameD.SELECT Sname
FROM S FROM S,SPJ
WHERE EXISTS WHERE S.Sno=SPJ.Sno
(SELECT * AND SPJ.Pno=’P3’)
FROM SPJ GROUP BY Sname
WHERE S.Sno=SPJ.Sno
AND SPJ.Pno=’P3’)
(18) A.∏sname(S)D?σPno=’P3’(SPJ)
B.∏sname(SD?σPno=’P3’(SPJ))
C.∏sname(S)-∏sname(σPno≠’P3’(S ?(SPJ)
D.∏sname(S)-∏sname((S ?σPno≠’P3’(SPJ)
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