国家开放大学(电大)《数据库应用技术》形考作业答案2

• A.左外连接

• B.右外连接

• C.内连接

• D.自连接

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• A.SUM(列名)

• B.MAX(列名)

• C.AVG(列名)

• D.COUNT(*)

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• A.SELECT Sno,COUNT(*)FROM SC GROUP BY Sno

• B.SELECT Sno FROM sC GROUP BY Sno WHERE COUNT(*)> 3

• C.SELECT Sno FROM sC GROUP BY Sno HAVING COUNT (*) >3

• D.SELECT Sno FROM sC GROUP BY Sno

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• A.SELECT Sname，MIN(Sage) FROM Student

• B.SELECT Sname，Sage FROM Student WHERESage = MIN(Sage)

• C.SELECT TOP 1 Sname，Sage FROM Student

• D.SELECTTOP 1 Sname，Sage FROM Student ORDER BY Sage

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• A.Case Grade when 90~100 THEN ’优"When 80~89 THEN'良’When 70~79 THEN’中”When 60~69 THEN'及格’Else '不及格’End

• B.Case When Gradebetween 90 and 100 THEN Grade =”优'When Grade between 80 and 89 THENGrade =’良”when Grade between 70 and 79THEN Grade = '中”When Grade between 60 and 69 THEN Grade =’及格”Else Grade = '不及格’End

• C.Case When Grade between 90 and 100THEN ’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’End

• D.Case Grade When 90~100 THEN Grade =”优”When 80~89 THEN Grade = ’良’When 70~79 THEN Grade ='中’When 60~69 THEN Grade = '及格’Else Grade = '不及格”End

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• A.ALTER

• B.SELECT

• C.UPDATE

• D.INSERT

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• A.INSERT INTO Teachers VALUES('T100”,”张宏”,NULL)

• B.INSERT INTO Teachers(Tno,Tname,Age)VALUES(”T100','张宏', 30)

• C.INSERT INTO Teachers(Tno, Tname)VALUES(”"T100”,'张宏')

• D.INSERT INTO Teachers VALUES (" T100’,'张宏’)

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• A.仅 Student表

• B.仅Student和SC表

• C.仅Student和 Course表

• D.Student、SC和Course表

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• A.DELETE FROM SC JOIN Student b oN s. Sno = SnoWHERESdept ='计算机系”

• B.DELETE FROM SC FROM sC JOIN Student b oN s Sno = SnoWHERE Sdept = '计算机系’

• C.DELETE FROM Student wHERE Sdept =’计算机系’

• D.DELETE FROMSCWHERESdept =’计算机系’

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• A.数据查询语句

• B.数据增、删、改语句

• C.创建表的语句

• D.全部都可以数据查询语句

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• A.外模式

• B.内模式

• C.模式

• D.其他外模式

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• A.提高数据查询效率

• B.维护数据的完整性约束

• C.维护数据的一致性

• D.提供用户视角的数据

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• A.CREATE VIEW vlAS SELECT所在系，COUNT(*)FROM学生表GROUP BY所在系

• B.CREATE VIEW vlAS SELECT所在系,SUM(*)FROM学生表GROUP BY所在系

• C.CREATE VIEW v1(系名,人数)AS SELECT所在系，SUM(*)FROM 学生表GROUP BY所在系

• D.CREATE VIEW v1(系名,人数)ASSELECT所在系,COUNT(*)FROM学生表GROUP BY所在系

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