北京广播电视大学数据库应用技术形考任务2-第5章测验0答案

1、试卷总分:30 得分:30一单项选择题（每题2分，共20分）当关系R和S进行连接操作时，如果R中的元组不满足连接条件，在连接结果中也会将这些记录保留下来的操作是（ ? ）。左外连接右外连接内连接自连接答案:A2.聚合函数中，不忽略空值的是（ ? ?）。? ? ?SUM(列名)MAX(列名)AVG(列名)COUNT(*)答案:D3.查询语句中，错误的是（ ? ?）。SELECT Sno, COUNT(*) FROM SC GROUP BY SnoSELECT Sno FROM SC GROUP BY Sno WHERE COUNT(*) 3SELECT Sno FROM SC GROUP BY

2、Sno HAVING COUNT(*) 3SELECT Sno FROM SC GROUP BY Sno答案:B4.现要利用Student表查询年龄最小的学生姓名和年龄。下列实现此功能的查询语句中，正确的是（ ? ?）。SELECT Sname, MIN(Sage) FROM StudentSELECT Sname, Sage FROM Student WHERE Sage = MIN(Sage)SELECT TOP 1 Sname, Sage FROM StudentSELECT TOP 1 Sname, Sage FROM Student ORDER BY Sage答案:D5.设SC表中记

3、录成绩的列为：Grade，类型为int。若在查询成绩时，希望将成绩按优、良、中、及格和不及格形式显示，正确的Case表达式是（ ? ）。Case GradeWhen 90100? THEN? 优When 8089? THEN? 良When 7079? THEN? 中When 6069? THEN? 及格Else? 不及格EndCaseWhen Grade? between 90 and 100? THEN? Grade = 优When Grade? between 80 and 89? THEN? Grade = 良When Grade? between 70 and 79? THEN? Gr

4、ade = 中When Grade? between 60 and 69? THEN? Grade = 及格Else? Grade = 不及格EndCaseWhen Grade? between 90 and 100? THEN? 优When Grade? between 80 and 89? THEN? 良When Grade? between 70 and 79? THEN? 中When Grade ?between 60 and 69? THEN? 及格Else? 不及格EndCase GradeWhen 90100? THEN Grade = 优When 8089? THEN Grad

5、e = 良When 7079? THEN Grade = 中When 6069? THEN Grade = 及格Else? Grade = 不及格? ?End答案:C6.在SQL语句中，用于更新表数据的语句是（ ? ）。ALTERSELECTUPDATEINSERT答案:C7.设有Teachers表，该表的定义如下：? CREATE TABLE Teachers(? ? Tno CHAR(8) PRIMARY KEY,? Tname VARCHAR(10) NOT NULL,? Age TINYINT CHECK(Age BETWEEN 25 AND 65) )插入语句中，不能正确执行的是（

6、? ）。INSERT INTO Teachers VALUES(T100,张宏,NULL)INSERT INTO Teachers(Tno,Tname,Age) VALUES(T100,张宏,30)INSERT INTO Teachers(Tno,Tname) VALUES(T100,张宏)INSERT INTO Teachers VALUES(T100,张宏)答案:D8.设数据库中已有表5-1至5-3所示的Student、Course和SC表。现要查询学生选的第2学期开设课程的情况，只需列出学号、姓名、所在系和所选的课程号。该查询涉及到的表是（ ? ）。仅Student表仅Student和S

7、C表仅Student和Course表Student、SC和Course表答案:D9.删除计算机系学生（在student表中）的修课记录（在SC表中）的语句，正确的是（ ? ）。DELETE? FROM SC JOIN Student b ON S.Sno = b.Sno? WHERE Sdept = 计算机系DELETE FROM SC FROM SC JOIN Student b ON SC.Sno = b.Sno? WHERE Sdept = 计算机系DELETE FROM Student? WHERE Sdept = 计算机系DELETE FROM SC WHERE Sdept = 计算

8、机系答案:B10.查询年龄最大的前5位学生的姓名和年龄的语句，正确的是（ ? ）。SELECT TOP 5 姓名, 年龄 FROM 学生表SELECT TOP 5 姓名, 年龄 FROM 学生表 ORDER BY 年龄SELECT TOP 5 姓名, 年龄 FROM 学生表 ORDER BY 年龄 DESCSELECT TOP 5 WITH TIES姓名, 年龄 FROM 学生表答案:C二判断题（每题2分，共10分）11.“SELECT * FROM Student WHERE Sname LIKE? 张_ ”语句中的张_ 用于查找姓张的学生。（ ? ?）答案:错误12.“SELECT * FROM Student WHERE Sname LIKE? 张李刘% ”语句可以查找姓张、李、刘的学生。（ ? ）答案:正确13.? “SELECT COUNT(DISTINCT Sno) FROM SC ”语句用于统计学生的总人数。（ ? ?）答案:错误14.HAVING子句用于对分组