50条常用SQL语句
要查询的数据库表和机构
Student(S#,Sname,Sage,Ssex) 学生表
Course(C#,Cname,T#) 课程表
SC(S#,C#,score) 成绩表
Teacher(T#,Tname) 教师表
问题：
1、查询“”课程比“”课程成绩高的所有学生的学号；
2、查询平均成绩大于分的同学的学号和平均成绩；
3、查询所有同学的学号、姓名、选课数、总成绩；
4、查询姓“李”的老师的个数；
5、查询没学过“叶平”老师课的同学的学号、姓名；
6、查询学过“”并且也学过编号“”课程的同学的学号、姓名；
7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
8、查询课程编号“”的成绩比课程编号“”课程低的所有同学的学号、姓名；
9、查询所有课程成绩小于分的同学的学号、姓名；
10、查询没有学全所有课的同学的学号、姓名；
11、查询至少有一门课与学号为“”的同学所学相同的同学的学号和姓名；
12、查询至少学过学号为“”同学所有一门课的其他同学学号和姓名；
13、把“SC”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩；
14、查询和“”号的同学学习的课程完全相同的其他同学学号和姓名；
15、删除学习“叶平”老师课的SC表记录；
16、向SC表中插入一些记录，这些记录要求符合以下条件：没有上过编号“”课程的同学学号、
号课的平均成绩；
17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示：学生ID,,数据库,企业管理,英语,有效课程数,有效平均分
18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分
19、按各科平均成绩从低到高和及格率的百分数从高到低顺序
20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理（），马克思（），OO&UML （），数据库（）
21、查询不同老师所教不同课程平均分从高到低显示
22、查询如下课程成绩第3 名到第6 名的学生成绩单：企业管理（），马克思（），UML （），数据库（）
[学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩
23、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]
24、查询学生平均成绩及其名次
25、查询各科成绩前三名的记录:(不考虑成绩并列情况)
26、查询每门课程被选修的学生数
27、查询出只选修了一门课程的全部学生的学号和姓名
28、查询男生、女生人数
29、查询姓“张”的学生名单
30、查询同名同性学生名单，并统计同名人数
31、年出生的学生名单(注：Student表中Sage列的类型是datetime)
32、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列
33、查询平均成绩大于的所有学生的学号、姓名和平均成绩
34、查询课程名称为“数据库”，且分数低于的学生姓名和分数
35、查询所有学生的选课情况；
36、查询任何一门课程成绩在分以上的姓名、课程名称和分数；
37、查询不及格的课程，并按课程号从大到小排列
38、查询课程编号为且课程成绩在分以上的学生的学号和姓名；
39、求选了课程的学生人数
40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩
41、查询各个课程及相应的选修人数
42、查询不同课程成绩相同的学生的学号、课程号、学生成绩
43、查询每门功成绩最好的前两名
44、统计每门课程的学生选修人数（超过人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，查询结果按人数降序排列，若人数相同，按课程号升序排列
45、检索至少选修两门课程的学生学号
46、查询全部学生都选修的课程的课程号和课程名
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
48、查询两门以上不及格课程的同学的学号及其平均成绩
49、检索“”课程分数小于，按分数降序排列的同学学号
50、删除“”同学的“”课程的成绩
转自：http://blog.csdn.net/fredrickhu/archive/2009/09/25/4592668.aspx
Student(S#,Sname,Sage,Ssex) 学生表
Course(C#,Cname,T#) 课程表
SC(S#,C#,score) 成绩表
Teacher(T#,Tname) 教师表
问题：
1、查询“”课程比“”课程成绩高的所有学生的学号；
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-SQL
SELECT a.S# FROM (SELECT s#,score FROM SC WHERE C#='001') a,
(SELECT s#,score FROM SC WHERE C#='002') b
WHERE a.score>b.score AND a.s#=b.s#;
(SELECT s#,score FROM SC WHERE C#='002') b
WHERE a.score>b.score AND a.s#=b.s#;
2、查询平均成绩大于分的同学的学号和平均成绩；
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-SQL
SELECT S#,avg(score)
FROM sc
GROUP BY S# having avg(score) >60;
FROM sc
GROUP BY S# having avg(score) >60;
3、查询所有同学的学号、姓名、选课数、总成绩；
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-SQL
SELECT Student.S#,Student.Sname,count(SC.C#),sum(score)
FROM Student left Outer JOIN SC on Student.S#=SC.S#
GROUP BY Student.S#,Sname
FROM Student left Outer JOIN SC on Student.S#=SC.S#
GROUP BY Student.S#,Sname
4、查询姓“李”的老师的个数；
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-SQL
SELECT count(distinct(Tname))
FROM Teacher
WHERE Tname like '李%';
FROM Teacher
WHERE Tname like '李%';
5、查询没学过“叶平”老师课的同学的学号、姓名；
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-SQL
SELECT Student.S#,Student.Sname
FROM Student
WHERE S# not in (SELECT distinct( SC.S#) FROM SC,Course,Teacher WHERE SC.C#=Course.C# AND Teacher.T#=Course.T# AND Teacher.Tname='叶平');
FROM Student
WHERE S# not in (SELECT distinct( SC.S#) FROM SC,Course,Teacher WHERE SC.C#=Course.C# AND Teacher.T#=Course.T# AND Teacher.Tname='叶平');
6、查询学过“”并且也学过编号“”课程的同学的学号、姓名；
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-SQL
SELECT Student.S#,Student.Sname FROM Student,SC WHERE Student.S#=SC.S# AND SC.C#='001'and exists( SELECT * FROM SC as SC_2 WHERE SC_2.S#=SC.S# AND SC_2.C#='002');
7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
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-SQL
SELECT S#,Sname
FROM Student
WHERE S# in (SELECT S# FROM SC ,Course ,Teacher WHERE SC.C#=Course.C# AND Teacher.T#=Course.T# AND Teacher.Tname='叶平' GROUP BY S# having count(SC.C#)=(SELECT count(C#) FROM Course,Teacher WHERE Teacher.T#=Course.T# AND Tname='叶平'));
FROM Student
WHERE S# in (SELECT S# FROM SC ,Course ,Teacher WHERE SC.C#=Course.C# AND Teacher.T#=Course.T# AND Teacher.Tname='叶平' GROUP BY S# having count(SC.C#)=(SELECT count(C#) FROM Course,Teacher WHERE Teacher.T#=Course.T# AND Tname='叶平'));
8、查询课程编号“”的成绩比课程编号“”课程低的所有同学的学号、姓名；
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-SQL
SELECT S#,Sname FROM (SELECT Student.S#,Student.Sname,score ,(SELECT score FROM SC SC_2 WHERE SC_2.S#=Student.S# AND SC_2.C#='002') score2
FROM Student,SC WHERE Student.S#=SC.S# AND C#='001') S_2 WHERE score2 <score;
FROM Student,SC WHERE Student.S#=SC.S# AND C#='001') S_2 WHERE score2 <score;
9、查询所有课程成绩小于分的同学的学号、姓名；
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-SQL
SELECT S#,Sname
FROM Student
WHERE S# not in (SELECT Student.S# FROM Student,SC WHERE S.S#=SC.S# AND score>60);
FROM Student
WHERE S# not in (SELECT Student.S# FROM Student,SC WHERE S.S#=SC.S# AND score>60);
10、查询没有学全所有课的同学的学号、姓名；
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-SQL
SELECT Student.S#,Student.Sname
FROM Student,SC
WHERE Student.S#=SC.S# GROUP BY Student.S#,Student.Sname having count(C#) <(SELECT count(C#) FROM Course);
FROM Student,SC
WHERE Student.S#=SC.S# GROUP BY Student.S#,Student.Sname having count(C#) <(SELECT count(C#) FROM Course);
11、查询至少有一门课与学号为“”的同学所学相同的同学的学号和姓名；
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-SQL
SELECT S#,Sname FROM Student,SC WHERE Student.S#=SC.S# AND C# in SELECT C# FROM SC WHERE S#='1001';
12、查询至少学过学号为“”同学所有一门课的其他同学学号和姓名；
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-SQL
SELECT distinct SC.S#,Sname
FROM Student,SC
WHERE Student.S#=SC.S# AND C# in (SELECT C# FROM SC WHERE S#='001');
FROM Student,SC
WHERE Student.S#=SC.S# AND C# in (SELECT C# FROM SC WHERE S#='001');
13、把“SC”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩；
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-SQL
update SC set score=(SELECT avg(SC_2.score)
FROM SC SC_2
WHERE SC_2.C#=SC.C# ) FROM Course,Teacher WHERE Course.C#=SC.C# AND Course.T#=Teacher.T# AND Teacher.Tname='叶平');
FROM SC SC_2
WHERE SC_2.C#=SC.C# ) FROM Course,Teacher WHERE Course.C#=SC.C# AND Course.T#=Teacher.T# AND Teacher.Tname='叶平');
14、查询和“”号的同学学习的课程完全相同的其他同学学号和姓名；
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-SQL
SELECT S# FROM SC WHERE C# in (SELECT C# FROM SC WHERE S#='1002')
GROUP BY S# having count(*)=(SELECT count(*) FROM SC WHERE S#='1002');
GROUP BY S# having count(*)=(SELECT count(*) FROM SC WHERE S#='1002');
15、删除学习“叶平”老师课的SC表记录；
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-SQL
Delect SC
FROM course ,Teacher
WHERE Course.C#=SC.C# AND Course.T#= Teacher.T# AND Tname='叶平';
FROM course ,Teacher
WHERE Course.C#=SC.C# AND Course.T#= Teacher.T# AND Tname='叶平';
16、向SC表中插入一些记录，这些记录要求符合以下条件：没有上过编号“”课程的同学学号、
号课的平均成绩；
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-SQL
Insert SC SELECT S#,'002',(SELECT avg(score)
FROM SC WHERE C#='002') FROM Student WHERE S# not in (SELECT S# FROM SC WHERE C#='002');
FROM SC WHERE C#='002') FROM Student WHERE S# not in (SELECT S# FROM SC WHERE C#='002');
17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示：学生ID,,数据库,企业管理,英语,有效课程数,有效平均分
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-SQL
SELECT S# as 学生ID
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='004') AS 数据库
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='001') AS 企业管理
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='006') AS 英语
,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩
FROM SC AS t
GROUP BY S#
ORDER BY avg(t.score)
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='004') AS 数据库
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='001') AS 企业管理
,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='006') AS 英语
,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩
FROM SC AS t
GROUP BY S#
ORDER BY avg(t.score)
18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分
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-SQL
SELECT L.C# As 课程ID,L.score AS 最高分,R.score AS 最低分
FROM SC L ,SC AS R
WHERE L.C# = R.C# AND
L.score = (SELECT MAX(IL.score)
FROM SC AS IL,Student AS IM
WHERE L.C# = IL.C# AND IM.S#=IL.S#
GROUP BY IL.C#)
AND
R.Score = (SELECT MIN(IR.score)
FROM SC AS IR
WHERE R.C# = IR.C#
GROUP BY IR.C#
);
FROM SC L ,SC AS R
WHERE L.C# = R.C# AND
L.score = (SELECT MAX(IL.score)
FROM SC AS IL,Student AS IM
WHERE L.C# = IL.C# AND IM.S#=IL.S#
GROUP BY IL.C#)
AND
R.Score = (SELECT MIN(IR.score)
FROM SC AS IR
WHERE R.C# = IR.C#
GROUP BY IR.C#
);
19、按各科平均成绩从低到高和及格率的百分数从高到低顺序
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-SQL
SELECT t.C# AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩
,100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数
FROM SC T,Course
WHERE t.C#=course.C#
GROUP BY t.C#
ORDER BY 100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC
,100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数
FROM SC T,Course
WHERE t.C#=course.C#
GROUP BY t.C#
ORDER BY 100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC
20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理（），马克思（），OO&UML （），数据库（）
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-SQL
SELECT SUM(CASE WHEN C# ='001' THEN score ELSE 0 END)/SUM(CASE C# WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分
,100 * SUM(CASE WHEN C# = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数
,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分
,100 * SUM(CASE WHEN C# = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数
,SUM(CASE WHEN C# = '003' THEN score ELSE 0 END)/SUM(CASE C# WHEN '003' THEN 1 ELSE 0 END) AS UML平均分
,100 * SUM(CASE WHEN C# = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '003' THEN 1 ELSE 0 END) AS UML及格百分数
,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分
,100 * SUM(CASE WHEN C# = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '004' THEN 1 ELSE 0 END) AS 数据库及格百分数
FROM SC
,100 * SUM(CASE WHEN C# = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数
,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分
,100 * SUM(CASE WHEN C# = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数
,SUM(CASE WHEN C# = '003' THEN score ELSE 0 END)/SUM(CASE C# WHEN '003' THEN 1 ELSE 0 END) AS UML平均分
,100 * SUM(CASE WHEN C# = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '003' THEN 1 ELSE 0 END) AS UML及格百分数
,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分
,100 * SUM(CASE WHEN C# = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '004' THEN 1 ELSE 0 END) AS 数据库及格百分数
FROM SC
21、查询不同老师所教不同课程平均分从高到低显示
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-SQL
SELECT max(Z.T#) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.C# AS 课程ＩＤ,MAX(C.Cname) AS 课程名称,AVG(Score) AS 平均成绩
FROM SC AS T,Course AS C ,Teacher AS Z
WHERE T.C#=C.C# AND C.T#=Z.T#
GROUP BY C.C#
ORDER BY AVG(Score) DESC
FROM SC AS T,Course AS C ,Teacher AS Z
WHERE T.C#=C.C# AND C.T#=Z.T#
GROUP BY C.C#
ORDER BY AVG(Score) DESC
22、查询如下课程成绩第3 名到第6 名的学生成绩单：企业管理（），马克思（），UML （），数据库（）
[学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩
+展开
-SQL
SELECT DISTINCT top 3
SC.S# As 学生学号,
Student.Sname AS 学生姓名,
T1.score AS 企业管理,
T2.score AS 马克思,
T3.score AS UML,
T4.score AS 数据库,
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分
FROM Student,SC LEFT JOIN SC AS T1
ON SC.S# = T1.S# AND T1.C# = '001'
LEFT JOIN SC AS T2
ON SC.S# = T2.S# AND T2.C# = '002'
LEFT JOIN SC AS T3
ON SC.S# = T3.S# AND T3.C# = '003'
LEFT JOIN SC AS T4
ON SC.S# = T4.S# AND T4.C# = '004'
WHERE student.S#=SC.S# AND
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
NOT IN
(SELECT
DISTINCT
TOP 15 WITH TIES
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
FROM sc
LEFT JOIN sc AS T1
ON sc.S# = T1.S# AND T1.C# = 'k1'
LEFT JOIN sc AS T2
ON sc.S# = T2.S# AND T2.C# = 'k2'
LEFT JOIN sc AS T3
ON sc.S# = T3.S# AND T3.C# = 'k3'
LEFT JOIN sc AS T4
ON sc.S# = T4.S# AND T4.C# = 'k4'
ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);
SC.S# As 学生学号,
Student.Sname AS 学生姓名,
T1.score AS 企业管理,
T2.score AS 马克思,
T3.score AS UML,
T4.score AS 数据库,
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分
FROM Student,SC LEFT JOIN SC AS T1
ON SC.S# = T1.S# AND T1.C# = '001'
LEFT JOIN SC AS T2
ON SC.S# = T2.S# AND T2.C# = '002'
LEFT JOIN SC AS T3
ON SC.S# = T3.S# AND T3.C# = '003'
LEFT JOIN SC AS T4
ON SC.S# = T4.S# AND T4.C# = '004'
WHERE student.S#=SC.S# AND
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
NOT IN
(SELECT
DISTINCT
TOP 15 WITH TIES
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
FROM sc
LEFT JOIN sc AS T1
ON sc.S# = T1.S# AND T1.C# = 'k1'
LEFT JOIN sc AS T2
ON sc.S# = T2.S# AND T2.C# = 'k2'
LEFT JOIN sc AS T3
ON sc.S# = T3.S# AND T3.C# = 'k3'
LEFT JOIN sc AS T4
ON sc.S# = T4.S# AND T4.C# = 'k4'
ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);
23、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]
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-SQL
SELECT SC.C# as 课程ID, Cname as 课程名称
,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85]
,SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70]
,SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60]
,SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -]
FROM SC,Course
WHERE SC.C#=Course.C#
GROUP BY SC.C#,Cname;
,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85]
,SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70]
,SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60]
,SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -]
FROM SC,Course
WHERE SC.C#=Course.C#
GROUP BY SC.C#,Cname;
24、查询学生平均成绩及其名次
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-SQL
SELECT 1+(SELECT COUNT( distinct 平均成绩)
FROM (SELECT S#,AVG(score) AS 平均成绩
FROM SC
GROUP BY S#
) AS T1
WHERE 平均成绩> T2.平均成绩) as 名次,
S# as 学生学号,平均成绩
FROM (SELECT S#,AVG(score) 平均成绩
FROM SC
GROUP BY S#
) AS T2
ORDER BY 平均成绩desc;
FROM (SELECT S#,AVG(score) AS 平均成绩
FROM SC
GROUP BY S#
) AS T1
WHERE 平均成绩> T2.平均成绩) as 名次,
S# as 学生学号,平均成绩
FROM (SELECT S#,AVG(score) 平均成绩
FROM SC
GROUP BY S#
) AS T2
ORDER BY 平均成绩desc;
25、查询各科成绩前三名的记录:(不考虑成绩并列情况)
+展开
-SQL
SELECT t1.S# as 学生ID,t1.C# as 课程ID,Score as 分数
FROM SC t1
WHERE score IN (SELECT TOP 3 score
FROM SC
WHERE t1.C#= C#
ORDER BY score DESC
)
ORDER BY t1.C#;
FROM SC t1
WHERE score IN (SELECT TOP 3 score
FROM SC
WHERE t1.C#= C#
ORDER BY score DESC
)
ORDER BY t1.C#;
26、查询每门课程被选修的学生数
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-SQL
SELECT c#,count(S#) FROM sc GROUP BY C#;
27、查询出只选修了一门课程的全部学生的学号和姓名
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-SQL
SELECT SC.S#,Student.Sname,count(C#) AS 选课数
FROM SC ,Student
WHERE SC.S#=Student.S# GROUP BY SC.S# ,Student.Sname having count(C#)=1;
FROM SC ,Student
WHERE SC.S#=Student.S# GROUP BY SC.S# ,Student.Sname having count(C#)=1;
28、查询男生、女生人数
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-SQL
SELECT count(Ssex) as 男生人数FROM Student GROUP BY Ssex having Ssex='男';
SELECT count(Ssex) as 女生人数FROM Student GROUP BY Ssex having Ssex='女'；
SELECT count(Ssex) as 女生人数FROM Student GROUP BY Ssex having Ssex='女'；
29、查询姓“张”的学生名单
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-SQL
SELECT Sname FROM Student WHERE Sname like '张%';
30、查询同名同性学生名单，并统计同名人数
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-SQL
SELECT Sname,count(*) FROM Student GROUP BY Sname having count(*)>1;
31、年出生的学生名单(注：Student表中Sage列的类型是datetime)
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-SQL
SELECT Sname, CONVERT(char (11),DATEPART(year,Sage)) as age
FROM student
WHERE CONVERT(char(11),DATEPART(year,Sage))='1981';
FROM student
WHERE CONVERT(char(11),DATEPART(year,Sage))='1981';
32、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列
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-SQL
SELECT C#,Avg(score) FROM SC GROUP BY C# ORDER BY Avg(score),C# DESC ;
33、查询平均成绩大于的所有学生的学号、姓名和平均成绩
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-SQL
SELECT Sname,SC.S# ,avg(score)
FROM Student,SC
WHERE Student.S#=SC.S# GROUP BY SC.S#,Sname having avg(score)>85;
FROM Student,SC
WHERE Student.S#=SC.S# GROUP BY SC.S#,Sname having avg(score)>85;
34、查询课程名称为“数据库”，且分数低于的学生姓名和分数
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-SQL
SELECT Sname,isnull(score,0)
FROM Student,SC,Course
WHERE SC.S#=Student.S# AND SC.C#=Course.C# AND Course.Cname='数据库'and score <60;
FROM Student,SC,Course
WHERE SC.S#=Student.S# AND SC.C#=Course.C# AND Course.Cname='数据库'and score <60;
35、查询所有学生的选课情况；
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-SQL
SELECT SC.S#,SC.C#,Sname,Cname
FROM SC,Student,Course
WHERE SC.S#=Student.S# AND SC.C#=Course.C# ;
FROM SC,Student,Course
WHERE SC.S#=Student.S# AND SC.C#=Course.C# ;
36、查询任何一门课程成绩在分以上的姓名、课程名称和分数；
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-SQL
SELECT distinct student.S#,student.Sname,SC.C#,SC.score
FROM student,Sc
WHERE SC.score>=70 AND SC.S#=student.S#;
FROM student,Sc
WHERE SC.score>=70 AND SC.S#=student.S#;
37、查询不及格的课程，并按课程号从大到小排列
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-SQL
SELECT c# FROM sc WHERE scor e <60 ORDER BY C# ;
38、查询课程编号为且课程成绩在分以上的学生的学号和姓名；
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-SQL
SELECT SC.S#,Student.Sname FROM SC,Student WHERE SC.S#=Student.S# AND Score>80 AND C#='003';
39、求选了课程的学生人数
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-SQL
SELECT count(*) FROM sc;
40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩
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-SQL
SELECT Student.Sname,score
FROM Student,SC,Course C,Teacher
WHERE Student.S#=SC.S# AND SC.C#=C.C# AND C.T#=Teacher.T# AND Teacher.Tname='叶平' AND SC.score=(SELECT max(score)FROM SC WHERE C#=C.C# );
FROM Student,SC,Course C,Teacher
WHERE Student.S#=SC.S# AND SC.C#=C.C# AND C.T#=Teacher.T# AND Teacher.Tname='叶平' AND SC.score=(SELECT max(score)FROM SC WHERE C#=C.C# );
41、查询各个课程及相应的选修人数
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-SQL
SELECT count(*) FROM sc GROUP BY C#;
42、查询不同课程成绩相同的学生的学号、课程号、学生成绩
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-SQL
SELECT distinct A.S#,B.score FROM SC A ,SC B WHERE A.Score=B.Score AND A.C# <>B.C# ;
43、查询每门功成绩最好的前两名
+展开
-SQL
SELECT t1.S# as 学生ID,t1.C# as 课程ID,Score as 分数
FROM SC t1
WHERE score IN (SELECT TOP 2 score
FROM SC
WHERE t1.C#= C#
ORDER BY score DESC
)
ORDER BY t1.C#;
FROM SC t1
WHERE score IN (SELECT TOP 2 score
FROM SC
WHERE t1.C#= C#
ORDER BY score DESC
)
ORDER BY t1.C#;
44、统计每门课程的学生选修人数（超过人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，查询结果按人数降序排列，若人数相同，按课程号升序排列
+展开
-SQL
SELECT C# as 课程号,count(*) as 人数
FROM sc
group by C#
order by count(*) desc,c#
FROM sc
group by C#
order by count(*) desc,c#
45、检索至少选修两门课程的学生学号
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-SQL
SELECT S#
FROM sc
group by s#
having count(*) > = 2
FROM sc
group by s#
having count(*) > = 2
46、查询全部学生都选修的课程的课程号和课程名
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-SQL
SELECT C#,Cname
FROM Course
WHERE C# in (SELECT c# FROM sc group by c#)
FROM Course
WHERE C# in (SELECT c# FROM sc group by c#)
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
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-SQL
SELECT Sname FROM Student WHERE S# not in (SELECT S# FROM Course,Teacher,SC WHERE Course.T#=Teacher.T# AND SC.C#=course.C# AND Tname='叶平');
48、查询两门以上不及格课程的同学的学号及其平均成绩
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-SQL
SELECT S#,avg(isnull(score,0)) FROM SC WHERE S# in (SELECT S# FROM SC WHERE score <60 GROUP BY S# having count(*)>2)GROUP BY S#;
49、检索“”课程分数小于，按分数降序排列的同学学号
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-SQL
SELECT S# FROM SC WHERE C#='004'and score <60 ORDER BY score desc;
50、删除“”同学的“”课程的成绩
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-SQL
delete FROM Sc WHERE S#='001'and C#='001';
转自：http://blog.csdn.net/fredrickhu/archive/2009/09/25/4592668.aspx
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