许久收藏的练习mysql语句的，现在看来任然有学习价值！
表如下：
- Student(Sid,Sname,Sage,Ssex) 学生表
- Course(Cid,Cname,Tid) 课程表
- SC(Sid,Cid,score) 成绩表
- Teacher(Tid,Tname) 教师表
问题：
1、查询“001”课程比“002”课程成绩高的所有学生的学号
select a.Sid from (select sid,score from SC where Cid='001') a,(select sid,score
from SC where Cid='002') b
where a.score>b.score and a.sid=b.sid;
2、查询平均成绩大于60分的同学的学号和平均成绩；
select Sid,avg(score)
from sc
group by Sid having avg(score) >60;
3、查询所有同学的学号、姓名、选课数、总成绩；
select Student.Sid,Student.Sname,count(SC.Cid),sum(score)
from Student left Outer join SC on Student.Sid=SC.Sid
group by Student.Sid,Sname ；
4、查询姓“李”的老师的个数；
select count(distinct(Tname))
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；
select Student.Sid,Student.Sname
from Student
where Sid not in (select distinct( SC.Sid) from SC,Course,Teacher
where SC.Cid=Course.Cid and Teacher.Tid=Course.Tid and Teacher.Tname='叶平');
6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
select Student.Sid,Student.Sname from Student,SC
where Student.Sid=SC.Sid and SC.Cid='001'and
exists( Select * from SC as SC_2 where SC_2.Sid=SC.Sid and SC_2.Cid='002');
7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
select Sid,Sname
from Student
where Sid in (select Sid from SC ,Course ,Teacher
where SC.Cid=Course.Cid and Teacher.Tid=Course.Tid and Teacher.Tname='叶平'
group by Sid having count(SC.Cid)=(select count(Cid) from Course,Teacher
where Teacher.Tid=Course.Tid and Tname='叶平'));
8、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；
26 Select Sid,Sname from (select Student.Sid,Student.Sname,score ,(select score from SC SC_2
27 where SC_2.Sid=Student.Sid and SC_2.Cid='002') score2
28 from Student,SC where Student.Sid=SC.Sid and Cid='001') S_2 where score2 <score;
9、查询所有课程成绩小于60分的同学的学号、姓名；
29 select Sid,Sname
30 from Student
31 where Sid not in (select Student.Sid from Student,SC where S.Sid=SC.Sid and score>60);
10、查询没有学全所有课的同学的学号、姓名；
32 select Student.Sid,Student.Sname
33 from Student,SC
34 where Student.Sid=SC.Sid
35 group by Student.Sid,Student.Sname having count(Cid) <(select count(Cid) from Course);
11、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；
36 select Sid,Sname from Student,SC
37 where Student.Sid=SC.Sid and Cid in select Cid from SC where Sid='1001';
12、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名；
38 select distinct SC.Sid,Sname
39 from Student,SC
40 where Student.Sid=SC.Sid and Cid in (select Cid from SC where Sid='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；
41 update SC set score=(select avg(SC_2.score)
42 from SC SC_2
43 where SC_2.Cid=SC.Cid ) from Course,Teacher
44 where Course.Cid=SC.Cid and Course.Tid=Teacher.Tid and Teacher.Tname='叶平');
14、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名；
45 select Sid from SC where Cid in (select Cid from SC where Sid='1002')
46 group by Sid having count(*)=(select count(*) from SC where Sid='1002');
15、删除学习“叶平”老师课的SC表记录；
47 Delect SC
48 from course ,Teacher
49 where Course.Cid=SC.Cid and Course.Tid= Teacher.Tid 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“003”课程的同学学号、2、号课的平均成绩；
50 Insert SC select Sid,'002',(Select avg(score)
51 from SC where Cid='002') from Student
52 where Sid not in (Select Sid from SC where Cid='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
53 SELECT Sid as 学生ID
54 ,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid='004') AS 数据库
55 ,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid='001') AS 企业管理
56 ,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid='006') AS 英语
57 ,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩
58 FROM SC AS t
59 GROUP BY Sid
60 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
61 SELECT L.Cid As 课程ID,L.score AS 最高分,R.score AS 最低分
62 FROM SC L ,SC AS R
63 WHERE L.Cid = R.Cid and
64 L.score = (SELECT MAX(IL.score)
65 FROM SC AS IL,Student AS IM
66 WHERE L.Cid = IL.Cid and IM.Sid=IL.Sid
67 GROUP BY IL.Cid)
68 AND
69 R.Score = (SELECT MIN(IR.score)
70 FROM SC AS IR
71 WHERE R.Cid = IR.Cid
72 GROUP BY IR.Cid
73 );
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
74 SELECT t.Cid AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩
75 ,100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数
76 FROM SC T,Course
77 where t.Cid=course.Cid
78 GROUP BY t.Cid
79 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（001），马克思（002），OO&UML （003），数据库（004）
80 SELECT SUM(CASE WHEN Cid ='001' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分
81 ,100 * SUM(CASE WHEN Cid = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数
82 ,SUM(CASE WHEN Cid = '002' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分
83 ,100 * SUM(CASE WHEN Cid = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数
84 ,SUM(CASE WHEN Cid = '003' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '003' THEN 1 ELSE 0 END) AS UML平均分
85 ,100 * SUM(CASE WHEN Cid = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid = '003' THEN 1 ELSE 0 END) AS UML及格百分数
86 ,SUM(CASE WHEN Cid = '004' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分
87 ,100 * SUM(CASE WHEN Cid = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid = '004' THEN 1 ELSE 0 END) AS 数据库及格百分数
88 FROM SC
21、查询不同老师所教不同课程平均分从高到低显示
89 SELECT max(Z.Tid) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.Cid AS 课程ID,MAX(C.Cname) AS 课程名称,AVG(Score) AS 平均成绩
90 FROM SC AS T,Course AS C ,Teacher AS Z
91 where T.Cid=C.Cid and C.Tid=Z.Tid
92 GROUP BY C.Cid
93 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（001），马克思（002），UML （003），数据库（004） [学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩
94 SELECT DISTINCT top 3
95 SC.Sid As 学生学号,
96 Student.Sname AS 学生姓名 ,
97 T1.score AS 企业管理,
98 T2.score AS 马克思,
99 T3.score AS UML,
100 T4.score AS 数据库,
101 ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分
102 FROM Student,SC LEFT JOIN SC AS T1
103 ON SC.Sid = T1.Sid AND T1.Cid = '001'
104 LEFT JOIN SC AS T2
105 ON SC.Sid = T2.Sid AND T2.Cid = '002'
106 LEFT JOIN SC AS T3
107 ON SC.Sid = T3.Sid AND T3.Cid = '003'
108 LEFT JOIN SC AS T4
109 ON SC.Sid = T4.Sid AND T4.Cid = '004'
110 WHERE student.Sid=SC.Sid and
111 ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
112 NOT IN
113 (SELECT
114 DISTINCT
115 TOP 15 WITH TIES
116 ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
117 FROM sc
118 LEFT JOIN sc AS T1
119 ON sc.Sid = T1.Sid AND T1.Cid = 'k1'
120 LEFT JOIN sc AS T2
121 ON sc.Sid = T2.Sid AND T2.Cid = 'k2'
122 LEFT JOIN sc AS T3
123 ON sc.Sid = T3.Sid AND T3.Cid = 'k3'
124 LEFT JOIN sc AS T4
125 ON sc.Sid = T4.Sid AND T4.Cid = 'k4'
126 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]
127 SELECT SC.Cid as 课程ID, Cname as 课程名称
128 ,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85]
129 ,SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70]
130 ,SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60]
131 ,SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -]
132 FROM SC,Course
133 where SC.Cid=Course.Cid
134 GROUP BY SC.Cid,Cname;
24、查询学生平均成绩及其名次
135 SELECT 1+(SELECT COUNT( distinct 平均成绩)
136 FROM (SELECT Sid,AVG(score) AS 平均成绩
137 FROM SC
138 GROUP BY Sid
139 ) AS T1
140 WHERE 平均成绩 > T2.平均成绩) as 名次,
141 Sid as 学生学号,平均成绩
142 FROM (SELECT Sid,AVG(score) 平均成绩
143 FROM SC
144 GROUP BY Sid
145 ) AS T2
146 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)
147 SELECT t1.Sid as 学生ID,t1.Cid as 课程ID,Score as 分数
148 FROM SC t1
149 WHERE score IN (SELECT TOP 3 score
150 FROM SC
151 WHERE t1.Cid= Cid
152 ORDER BY score DESC
153 )
154 ORDER BY t1.Cid;
26、查询每门课程被选修的学生数
155 select cid,count(Sid) from sc group by Cid;
27、查询出只选修了一门课程的全部学生的学号和姓名
156 select SC.Sid,Student.Sname,count(Cid) AS 选课数
157 from SC ,Student
158 where SC.Sid=Student.Sid group by SC.Sid ,Student.Sname having count(Cid)=1;
28、查询男生、女生人数
159 Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex='男';
160 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
161 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
162 select Sname,count(*) from Student group by Sname having count(*)>1;;
31、1981年出生的学生名单(注：Student表中Sage列的类型是datetime)
163 select Sname, CONVERT(char (11),DATEPART(year,Sage)) as age
164 from student
165 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
166 Select Cid,Avg(score) from SC group by Cid order by Avg(score),Cid DESC ;
33、查询平均成绩大于85的所有学生的学号、姓名和平均成绩
167 select Sname,SC.Sid ,avg(score)
168 from Student,SC
169 where Student.Sid=SC.Sid group by SC.Sid,Sname having avg(score)>85;
34、查询课程名称为“数据库”，且分数低于60的学生姓名和分数
170 Select Sname,isnull(score,0)
171 from Student,SC,Course
172 where SC.Sid=Student.Sid and SC.Cid=Course.Cid and Course.Cname='数据库'and score <60;
35、查询所有学生的选课情况；
173 SELECT SC.Sid,SC.Cid,Sname,Cname
174 FROM SC,Student,Course
175 where SC.Sid=Student.Sid and SC.Cid=Course.Cid ;
36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
176 SELECT distinct student.Sid,student.Sname,SC.Cid,SC.score
177 FROM student,Sc
178 WHERE SC.score>=70 AND SC.Sid=student.Sid;
37、查询不及格的课程，并按课程号从大到小排列
179 select cid from sc where scor e <60 order by Cid ;
38、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
180 select SC.Sid,Student.Sname from SC,Student
181 where SC.Sid=Student.Sid and Score>80 and Cid='003';
39、求选了课程的学生人数
182 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
183 select Student.Sname,score
184 from Student,SC,Course C,Teacher
185 where Student.Sid=SC.Sid and SC.Cid=C.Cid and C.Tid=Teacher.Tid and Teacher.Tname='叶平'
186 and SC.score=(select max(score)from SC where Cid=C.Cid );
41、查询各个课程及相应的选修人数
187 select count(*) from sc group by Cid;
42、查询不同课程成绩相同的学生的学号、课程号、学生成绩
188 select distinct A.Sid,B.score from SC A ,SC B where A.Score=B.Score and A.Cid <>B.Cid ;
43、查询每门功成绩最好的前两名
189 SELECT t1.Sid as 学生ID,t1.Cid as 课程ID,Score as 分数
190 FROM SC t1
191 WHERE score IN (SELECT TOP 2 score
192 FROM SC
193 WHERE t1.Cid= Cid
194 ORDER BY score DESC
195 )
196 ORDER BY t1.Cid;
44、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，查询结果按人数降序排列，若人数相同，按课程号升序排列
197 select Cid as 课程号,count(*) as 人数
198 from sc
199 group by Cid
200 order by count(*) desc,cid
45、检索至少选修两门课程的学生学号
201 select Sid
202 from sc
203 group by sid
204 having count(*) > = 2
46、查询全部学生都选修的课程的课程号和课程名
205 select Cid,Cname
206 from Course
207 where Cid in (select cid from sc group by cid)
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
208 select Sname from Student where Sid not in (select Sid from Course,Teacher,SC
209 where Course.Tid=Teacher.Tid and SC.Cid=course.Cid 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
210 select Sid,avg(isnull(score,0)) from SC
211 where Sid in (select Sid from SC where score <60
212 group by Sid having count(*)>2)group by Sid;
49、检索“004”课程分数小于60，按分数降序排列的同学学号
213 select Sid from SC where Cid='004'and score <60 order by score desc;
50、删除“002”同学的“001”课程的成绩
214 delete from Sc where Sid='001'and Cid='001';