数据库原理及应用习题参考答案

FROM SC

WHERE C# IN (SELECT C# FROM C

WHERE TEACHER=’LIU’))

或:

SELECT SNAME (存在量词方式) FROM S

WHERE SEX=’F’ AND EXISTS(SELECT* FROM SC

WHERE SC.S#=S.S# AND EXISTS(SELECT * FROM C

WHERE C.C#=SC.C# AND TEACHER=’LIU’))

⑸ SELECT C# FROM C

WHERE NOT EXISTS (SELECT * FROM S,SC

WHERE S.S#=SC.S# AND SC.C#=C.C# AND SNAME=’WANG)); ⑹ SELECT DISTINCT X.S# FROM SC AS X,SC AS Y

WHERE X.S#=Y.S# AND X.C#!=Y.C#; ⑺ SELECT C#.CNAME FROM C

WHERE NOT EXISTS (SELECT * FROM S

WHERE NOT EXISTS (SELECT * FROM SC

WHERE S#=S.S# AND C#=C.C#)); ⑻ SELECT DISTINCT S#

FROM SC AS X

WHERE NOT EXISTIS

(SELECT *

FROM C

WHERE TEACHER=’LIU’ AND NOT EXISTS (SELECT * FROM SC AS Y

WHERE Y.S#=X.S# AND Y.C#=C.C#));

4-3 试用SQL查询语句表达下列对4.2题中教务管理数据库的三个基本表S、SC、C查询: ⑴ 统计有学生选修的课程门数。

⑵ 求选修4号课程的学生的平均年龄。

⑶ 求LIU老师所授课程的每门课程的学生平均成绩。

第 8 页

⑷ 统计每门课程的学生选修人数(超过10人的课程才统计)。要求输出课程号和选修人数,查询结果按人数降序排列,若人数相同,按课程号升序排列。 ⑸ 检索学号比WANG同学大,而年龄比他小的学生姓名。 ⑹ 检索姓名以WANG打头的所有学生的姓名和年龄。 ⑺ 在SC中检索成绩为空值的学生学号和课程号。 ⑻ 求年龄大于女同学平均年龄的男学生姓名和年龄。

⑼ 求年龄大于所有女同学年龄的男学生姓名和年龄。

解:

⑴ SELECT COUNT(DISTINCT C#) FROM SC;

⑵ SELECT AVG(AGE) FROM S,SC

WHERE S.S#=SC.S# AND C#=’4’AND SEX=’F’; ⑶ SELECT C.C#,AVG(GRADE) FROM SC,C

WHERE SC.C#=C.C# AND TEACHER=’LIU’; ⑷ SELECT C#,COUNT(S#) FROM SC

GROUP BY C#

HAVING COUNT(*)>10

ORDER BY 2 DESC,1; ⑸ SELECT SNAME FROM S

WHERE S#>ALL(SELECT S# FROM S

WHERE SNAME=’WANG’

AND AGE

FROM S

WHERE SNAME=’WANG’); ⑹ SELECT SNAME,AGE FROM S

WHERE SNAME LIKE ‘WANG%’ ⑺ SELECT S#,C# FROM SC

WHERE GRADE IS NULL;

⑻ SELECT SNAME,AGE FROM S

WHERE SEX=’M’AND AGE>(SELECT AVG(AGE) FROM S

WHERE SEX=’F’);

⑼ SELECT SNAME,AGE FROM S

WHERE SEX=’M’AND AGE>ALL(SELECT AGE FROM S

第 9 页

WHERE SEX=’F’);

4-4 试用SQL更新语句表达对4.2给出的教务管理数据库中三个基本表S、SC、C进行如下更新操作:

⑴ 往基本表S中插入一个学生元组(‘200912143’,‘张晶’,21)。

⑵ 在基本表S中检索每一门课程成绩都大于等于80分的学生学号、姓名和性别,并把检索到的值送往另一个已存在的基本表STUDENT(SNO,SNAME,SEX)。 ⑶ 在基本表SC中删除尚无成绩的选课元组。 ⑷ 把张成民同学在SC中的选课记录全部删去。

⑸ 把选修高等数学课程中不及格的成绩全部改为空值。 ⑹ 把低于总平均成绩的女同学成绩提高5%。

⑺ 在基本表SC中修改4号课程的成绩,若成绩小于等于75分时提高5%,若成绩大于75分时提高4%(用两个UPDATE语句实现)。

解:

⑴INSERT INTO S(S#,SNAME,AGE) VALUES(‘200912143’,’张晶’,21);

INSERT INTO STUDENT⑵(SNO,SNAME,SEX) SELECT S#,SNAME,SEX FROM S

WHERE S# IN (SELECT S# FROM SC

WHERE 80<=ALL(SELECT GRADE

FROM SC

GROUP BY S#));

DELETE FROM SC⑶

WHERE GRADE IS NULL; DELE⑷TE FROM SC

WHERE S# IN(SELECT S# FROM S

WHERE SNAME=’张民’) ⑸UPDATE SC SET GRADE=NULL

WHERE GRADE<60 AND C# IN(SELECT C# FROM C

WHERE CNAME=’高等数学’); ⑹UPDATE SC

SET GRADE=GRADE*1.05 WHERE S# IN(SELECT S# FROM S

WHERE SEX=’F’)

AND GRADE<(SELECT AVG(GRADE) FROM SC);

⑺ 用两个UPDATE语句实现: UPDATE SC

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