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数据库原理及应用(29)

数据库原理及应用(29)

 

  6.设有关系R(A,B,C)和S(C,D)。与SQL语句nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  select A,B,D from R,S where R.C=S.C等价的关系代数表达式是( B )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)  σR.C=S.C(πA,B,D(R×S))nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  B)  πA,B,D(σR.C=S.C (R×S))nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C)  σR.C=S.C(πA,B(R)×πD(S))nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  D)  σR.C=S.C(πD(πA,B(R)×S))nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  7.在SQL语言的SELECT语句中,实现投影操作的是哪个子句( A )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)  select B) from C) where D) group bynd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  8.SQL的DROP INDEX语句的作用是( A )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)  删除索引 B)建立索引 C)修改索引 D)更新索引nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  9.在所有的关系数据库上的操作,( D )是核心,是其他操作的前提。nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)插入  B)删除  C)修改  D)查询nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  10.设两个关系C和SC如下,它们的主键分别为C#和(S#,C#)。若要向关系SC执行下列插入操作,( A )元组可以被插入。nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  Cnd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C#  CNAME  TEACHERnd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  c1nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  c2nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  c3  Databasend7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  Networknd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  OS  Zhangnd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  Lind7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  Wund7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  SCnd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  S#  C#  SCOREnd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  993001nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  991021nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  997345nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  993069  C1nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C3nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C2nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C3  88nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  78nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  95nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)  (‘993001’,‘C2’,null)  nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  B)  (‘994010’,’C4’,90)  nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C)(‘997345’,’C2’,65)nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  11.设有关系R(A,B,C),与SQL语句SELECT DISTINCT A FROM R WHERE B=17等价的关系代数表达式是( C )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)πA(R)        B)σB=17(R) nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C)πA(σB=17(R)) D)σB=17(πA(R))nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  12.SQL语言集数据定义、数据操纵和数据控制于一体,其中CREATE、DROP、ALTER语句是实现哪种功能的( A )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)数据定义   B)数据操纵   C)数据控制nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  13.SQL语言具有两种使用方式,分别称为交互式SQL和( C )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)  提示式SQL  B)多用户SQL  C)嵌入式SQL  D)解释式SQLnd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  14.在SQL中,基本表的撤销可以用( B )nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  A)  DROP SCHEMA命令   B)DROP TABLE 命令nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

  C)DROP VIEW命令      D)DROP INDEX命令nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app
nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

nd7湖南凯时app网_湖南凯时app本科_湖南凯时app报名_凯时app

 

数据库原理及应用(29)

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