数据库常用面试题
题目1:======
为管理岗位业务培训信息，建立3个表:
S (S#,SN,SD,SA) S#,SN,SD,SA 分别代表学号、学员姓名、所属单位、学员年龄
C (C#,CN ) C#,CN 分别代表课程编号、课程名称
SC ( S#,C#,G ) S#,C#,G 分别代表学号、所选修的课程编号、学习成绩
1. 使用标准SQL嵌套语句查询选修课程名称为 税收基础 的学员学号和姓名
Select SN,SD FROM S
Where IN ( Select FROM C,SC
Where C.=SC. AND CN=N'税收基础')
2. 使用标准SQL嵌套语句查询选修课程编号为’C2’的学员姓名和所属单位 Select S.SN,S.SD FROM S,SC
Where S.=SC. AND SC.='C2'
3. 使用标准SQL嵌套语句查询不选修课程编号为’C5’的学员姓名和所属单位 Select SN,SD FROM S
Where NOT IN
( Select FROM SC
Where ='C5')
4. 使用标准SQL嵌套语句查询选修全部课程的学员姓名和所属单位
网上流传的错误答案:
Select SN,SD FROM S
Where IN( Select FROM SC RIGHT JOIN
CON SC.=C.
GROUP BY
HAVING COUNT(*)=COUNT() )
经过调试验证的正确答案:
SELECT SN, SD FROM S
WHERE S#
IN (SELECT SC.S#
FROM SC RIGHT JOIN C
ON SC.C# = C.C#
GROUP BY SC.S#--在结果集中以学生分组，分组后的 SC.C#选课数=C.C#课程数 即为全部课程
HAVING COUNT(distinct(SC.C#))--注意：一个学生同一门课程可能有多条成绩记录,需要distinct
= ( select count(*) from C ) --注意：HAVING条件不能用COUNT(distinct(SC.C#)) = COUNT(distinct(C.C#)
)--子查询获得选修全部课程的学生学号
5. 查询选修了课程的学员人数 Select 学员人数=COUNT(DISTINCT ) FROM SC
6. 查询选修课程超过5门的学员学号和所属单位 Select SN,SD FROM S
Where IN (Select FROM SC
GROUP BY
HAVING COUNT( DISTINCT )> 5 )
题目2:
======
已知关系模式:
S (SNO,SNAME) 学生关系。SNO 为学号，SNAME 为姓名
C (CNO,CNAME,CTEACHER) 课程关系。CNO 为课程号，CNAME 为课程名，CTEACHER 为任课教师
SC(SNO,CNO,SCGRADE) 选课关系。SCGRADE 为成绩
1. 找出没有选修过“李明”老师讲授课程的所有学生姓名Select SNAME FROM S
Where NOT EXISTS ( Select * FROM SC,C
Where SC.CNO=C.CNO
AND CNAME='李明'
AND SC.SNO=S.SNO)
2. 列出有二门以上(含两门)不及格课程的学生姓名及其平均成绩 Select S.SNO,S.SNAME,AVG_SCGRADE=AVG(SC.SCGRADE)
FROMS ,SC ,
(Select SNO FROM SC
Where SCGRADE<60
GROUP BY SNO
HAVING COUNT(DISTINCT CNO)>=2) A
Where S.SNO=A.SNO AND SC.SNO=A.SNO
GROUP BY S.SNO,S.SNAME
3. 列出既学过“1”号课程，又学过“2”号课程的所有学生姓名 Select S.SNO,S.SNAME
FROM S,
(Select SC.SNOFROM SC,C
Where SC.CNO=C.CNO
AND C.CNAME IN('1','2')
GROUP BY SNO
HAVING COUNT(DISTINCT CNO)=2
)SC
Where S.SNO=SC.SNO
4. 列出“1”号课成绩比“2”号同学该门课成绩高的所有学生的学号 Select S.SNO,S.SNAME
FROM S,
(Select SC1.SNOFROM SC SC1,C C1,SC SC2,C C2
Where SC1.CNO=C1.CNO AND C1.NAME='1'
AND SC2.CNO=C2.CNO AND C2.NAME='2'
AND SC1.SCGRADE>SC2.SCGRADE)SC
Where S.SNO=SC.SNO
5. 列出“1”号课成绩比“2”号课成绩高的所有学生的学号及其“1”号课和“2”号课的成绩
Select S.SNO,S.SNAME,SC.,SC.
FROM S,
(Select SC1.SNO,=SC1.SCGRADE,=SC2.SCGRADE
FROM SC SC1,C C1,SC SC2,C C2
Where SC1.CNO=C1.CNO AND C1.NAME='1'
AND SC2.CNO=C2.CNO AND C2.NAME='2'
AND SC1.SCGRADE>SC2.SCGRADE) SC
Where S.SNO=SC.SNO
题目3:
======
有如下表记录:
ID Name EmailAddress LastLogon
100 test4 test4@yahoo.cn 2007-11-25 16:31:26
13 test1 test1@yahoo.cn 2007-3-22 16:27:07
19 test1 test1@yahoo.cn 2007-10-25 14:13:46
42 test1 test1@yahoo.cn 2007-11-20 14:20:10
45 test2 test2@yahoo.cn 2007-4-25 14:17:39
49 test2 test2@yahoo.cn 2007-5-25 14:22:36
用一句sql查询出每个用户最近一次登录的记录(每个用户只显示一条最近登录的记录)
方法一:
SELECT a.* from usersainner join
(SELECT , LastLogon=MAX(LastLogon) FROMusers GROUP BY )b
on a.=b. and a.=b.
方法二:
SELECT a.* from usersa inner join
(SELECTName,MAX(LogonID) LogonID FROMusers GROUP BY )b
on a.LogonID=b.LogonID
--where a.LogonId=b.LogonId
绿色通道：好文要顶关注我收藏该文与我联系
页:
[1]