面试必练：50道经典SQL练习

--1.学生表

--- Student(S,Sname,Sage,Ssex)

--S 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别

--2.课程表

-- Course(C,Cname,T)

--C --课程编号,Cname 课程名称,T 教师编号

--3.教师表

-- Teacher(T,Tname)

--T 教师编号,Tname 教师姓名

--4.成绩表

-- SC(S,C,score)

--S 学生编号,C 课程编号,score 分数

--创建测试数据

create table Student(S varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10));

insert into Student values('01' , '赵雷' , '1990-01-01' , '男');

insert into Student values('02' , '钱电' , '1990-12-21' , '男');

insert into Student values('03' , '孙风' , '1990-05-20' , '男');

insert into Student values('04' , '李云' , '1990-08-06' , '男');

insert into Student values('05' , '周梅' , '1991-12-01' , '女');

insert into Student values('06' , '吴兰' , '1992-03-01' , '女');

insert into Student values('07' , '郑竹' , '1989-07-01' , '女');

insert into Student values('08' , '王菊' , '1990-01-20' , '女');

--

create table Course(C varchar(10),Cname varchar(10),T varchar(10));

insert into Course values('01' , '语文' , '02');

insert into Course values('02' , '数学' , '01');

insert into Course values('03' , '英语' , '03');

--

create table Teacher(T varchar(10),Tname varchar(10));

insert into Teacher values('01' , '张三');

insert into Teacher values('02' , '李四');

insert into Teacher values('03' , '王五');

--

create table SC(S varchar(10),C varchar(10),score decimal(18,1));

insert into SC values('01' , '01' , 80);

insert into SC values('01' , '02' , 90);

insert into SC values('01' , '03' , 99);

insert into SC values('02' , '01' , 70);

insert into SC values('02' , '02' , 60);

insert into SC values('02' , '03' , 80);

insert into SC values('03' , '01' , 80);

insert into SC values('03' , '02' , 80);

insert into SC values('03' , '03' , 80);

insert into SC values('04' , '01' , 50);

insert into SC values('04' , '02' , 30);

insert into SC values('04' , '03' , 20);

insert into SC values('05' , '01' , 76);

insert into SC values('05' , '02' , 87);

insert into SC values('06' , '01' , 31);

insert into SC values('06' , '03' , 34);

insert into SC values('07' , '02' , 89);

insert into SC values('07' , '03' , 98);

--题目

--1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

--2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数

--3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩

--4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩

--5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

--6、查询"李"姓老师的数量

--7、查询学过"张三"老师授课的同学的信息

--8、查询没学过"张三"老师授课的同学的信息

--9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

--10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

--11、查询没有学全所有课程的同学的信息

--12、查询至少有一门课与学号为"01"的同学所学相同的同学的信息

--13、查询和"01"号的同学学习的课程完全相同的其他同学的信息

--14、查询没学过"张三"老师讲授的任一门课程的学生姓名

--15、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

--16、检索"01"课程分数小于60，按分数降序排列的学生信息

--17、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

--18、查询各科成绩最高分、最低分和平均分：以如下形式显示：

--课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率

--及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90

--19、按各科成绩进行排序，并显示排名

--20、查询学生的总成绩并进行排名

--21、查询不同老师所教不同课程平均分从高到低显示

--22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

--23、统计各科成绩各分数段人数：课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

--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

--26、查询每门课程被选修的学生数

--27、查询出只有两门课程的全部学生的学号和姓名

--28、查询男生、女生人数

--29、查询名字中含有"风"字的学生信息

--30、查询同名同性学生名单，并统计同名人数

--31、查询1990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，结果按平均成绩降序排列，平均成绩相同时，按课程编号

--33、查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩

--34、查询课程名称为"数学"，且分数低于60的学生姓名和分数

--35、查询所有学生的课程及分数情况；

--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；

--37、查询不及格的课程

--38、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；

--39、求每门课程的学生人数

--40、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩

--41、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

--42、查询每门功成绩最好的前两名

--43、统计每门课程的学生选修人数（超过5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  

--44、检索至少选修两门课程的学生学号

--45、查询选修了全部课程的学生信息

--46、查询各学生的年龄

--47、查询本周过生日的学生

--48、查询下周过生日的学生

--49、查询本月过生日的学生

--50、查询下月过生日的学生

--参考SQL

--1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

SELECT a.* ,c.* from (select a.*
from (SELECT * from sc WHERE sc.C in('01'))a left JOIN(SELECT * from sc where sc.C in('02'))b ON a.s =b.s where a.score>b.score ) a ,student c where a.s =c.s;

--2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数

SELECT a.* ,c.* FROM (SELECT a.* FROM (SELECT * FROM sc WHERE sc.C in('01'))a LEFT JOIN(SELECT * FROM sc WHERE sc.C in('02'))b ON a.s =b.s WHERE a.score<b.score) a,student c WHERE a.s =c.s

--3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩

SELECT b.s ,c.Sname ,b.avgscore FROM (SELECT a.s s , avg(a.score) avgscore FROM sc a GROUP BY a.s) b ,student c WHERE b.avgscore>60 AND c.s =b.s

--4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩

SELECT b.s ,c.Sname ,b.avgscore FROM (SELECT a.s s , avg(a.score) avgscore FROM sc a GROUP BY a.s) b ,student c WHERE b.avgscore<60 AND c.s =b.s

--5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

SELECT b.s ,c.Sname ,b.num ,b.sumscore FROM (SELECT a.s s ,COUNT(a.c) num ,SUM(a.score) sumscore FROM sc a GROUP BY a.s) b ,student c WHERE b.s =c.s

--6、查询"李"姓老师的数量

SELECT COUNT(a.Tname) FROM (SELECT Tname Tname FROM teacher WHERE Tname LIKE '李%') a

--7、查询学过"张三"老师授课的同学的信息

SELECT d.* FROM student d ,sc e WHERE e.S =d.S AND e.C= (SELECT b.C FROM teacher a ,course b WHERE a.T =b.T AND a.Tname='张三')

--8、查询没学过"张三"老师授课的同学的信息

SELECT a.* FROM student a WHERE a.S NOT in (SELECT b.S FROM sc a ,student b

WHERE a.S=b.S AND a.C = (SELECT b.c FROM teacher a ,course b WHERE a.T =b.T AND a.Tname ='张三'))

--9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

SELECT * FROM sc a, sc b, student c WHERE a.S =b.S AND a.C='01' and b.C='02'
AND c.S =a.S

--10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

SELECT * FROM student a WHERE a.S in ( SELECT DISTINCT(sc.s) FROM sc WHERE sc.S NOT in( SELECT S FROM sc WHERE sc.C in('02') GROUP BY sc.S) )

--11、查询没有学全所有课程的同学的信息

SELECT b.* FROM student b WHERE b.S in ( SELECT a.s FROM (SELECT a.S s ,COUNT(a.C) NUM FROM sc a GROUP BY a.s) a WHERE a.NUM<3 )

--12、查询至少有一门课与学号为"01"的同学所学相同的同学的信息

SELECT e.* FROM student e WHERE e.S in (SELECT DISTINCT(c.s) FROM student c ,sc d WHERE c.s=d.s AND d.C in (SELECT b.c FROM student a ,sc b WHERE a.s =b.s AND a.s ='01' ) )

--13、查询和"01"号的同学学习的课程完全相同的其他同学的信息

SELECT * FROM (SELECT a.* ,COUNT(b.c) num FROM student a ,sc b WHERE a.s=b.S GROUP BY b.S ) a WHERE a.num=3 AND a.s <> '01'

--14、查询没学过"张三"老师讲授的任一门课程的学生姓名

SELECT * FROM student a WHERE a.S NOT in ( SELECT b.S FROM ( SELECT b.c ,b.Cname FROM teacher a ,course b WHERE a.T=b.T AND a.Tname='张三' ) a ,sc b WHERE a.c=b.C )

--15、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

SELECT b.S ,b.Sname ,a.avgscore FROM (SELECT AVG(score) avgscore ,s S FROM sc WHERE sc.score<60 GROUP BY s HAVING COUNT(s)>=2) a ,student b WHERE a.S=b.S

--16、检索"01"课程分数小于60，按分数降序排列的学生信息

SELECT b.* FROM (SELECT a.s s FROM sc a WHERE a.C ='01' AND a.score<60 ORDER BY a.score DESC ) a ,student b WHERE a.s=b.S

--17、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

SELECT * FROM (SELECT b.S ,b.C ,b.score ,c.avgscore FROM sc b LEFT JOIN (SELECT a.S ,AVG(a.score) avgscore FROM sc a GROUP BY a.S) c ON c.S =b.S) a ,student b WHERE a.S =b.S ORDER BY avgscore DESC

--18、查询各科成绩最高分、最低分和平均分：以如下形式显示：

--课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率

--及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90

SELECT a.C ,b.Cname ,MAX(a.score) ,MIN(a.score) ,AVG(a.score) ,(SELECT COUNT(1) FROM sc WHERE sc.C=b.C and score>60)/(SELECT COUNT(1)FROM sc WHERE sc.C=b.c ) jigelv FROM sc a ,course b WHERE a.C =b.C GROUP BY a.C SELECT a.C ,a.Cname ,MAX(b.score) ,MIN(b.score) ,CAST(AVG(b.score) AS DECIMAL(18,2)) pingqunfen ,CAST((SELECT COUNT(1) FROM sc WHERE sc.C=a.C AND sc.score>60)/ (SELECT COUNT(1) FROM sc WHERE sc.C =a.C) AS DECIMAL(18,2)) jigelv ,CAST((SELECT COUNT(1) FROM sc WHERE sc.C =a.c AND sc.score>=70 AND sc.score<80)/ (SELECT COUNT(1) FROM sc WHERE sc.c =a.c) AS DECIMAL (18,2)) youlianlv FROM course a,sc b WHERE a.C=b.C GROUP BY a.C,a.Cname ORDER BY a.C DESC

--19、按各科成绩进行排序，并显示排名

SELECT c.s ,c.sname ,b.cname ,a.score ,(SELECT COUNT(1) FROM sc WHERE sc.C=a.c AND sc.score > a.score)+1 mc FROM sc a ,course b,student c WHERE a.c='01' AND a.c=b.c AND a.s=c.s ORDER BY mc SELECT c.s ,c.sname ,b.cname ,a.score ,(SELECT COUNT(1) FROM sc WHERE sc.C=a.c AND sc.score > a.score)+1 mc FROM sc a ,course b,student c WHERE a.c='02' AND a.c=b.c AND a.s=c.s ORDER BY mc SELECT c.s ,c.sname ,b.cname ,a.score ,(SELECT COUNT(1) FROM sc WHERE sc.C=a.c AND sc.score > a.score)+1 mc FROM sc a ,course b,student c WHERE a.c='03' AND a.c=b.c AND a.s=c.s ORDER BY mc

--20、查询学生的总成绩并进行排名

SELECT b.s ,b.sumscore ,@rownum:=@rownum +1 AS rownum FROM (SELECT a.s s ,SUM(a.score) sumscore FROM sc a GROUP BY a.S ORDER BY sumscore DESC ) as b ,(SELECT @rownum:=0)r

--21、查询不同老师所教不同课程平均分从高到低显示

SELECT c.Tname ,b.Cname ,AVG(a.score) FROM sc a ,course b ,teacher c WHERE a.C =b.C AND b.T =c.T GROUP BY a.C ORDER BY AVG(a.score) DESC

--22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

SELECT a.* ,b.* FROM (SELECT b.s ,b.C ,b.score ,(SELECT COUNT() FROM sc a WHERE a.c='01'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='01' HAVING mc BETWEEN 2 AND 3 UNION ALL SELECT b.s ,b.C ,b.score ,(SELECT COUNT() FROM sc a WHERE a.c='02'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='02' HAVING mc BETWEEN 2 AND 3 UNION ALL SELECT b.s ,b.C ,b.score ,(SELECT COUNT(*) FROM sc a WHERE a.c='03'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='03' HAVING mc BETWEEN 2 AND 3 ) a ,student b WHERE a.s =b.s

--23、统计各科成绩各分数段人数：课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

SELECT a.* FROM (SELECT c.Cname ,(SELECT COUNT()FROM sc a WHERE a.score>85 AND a.C=b.c AND c.c=a.C AND a.C='01') '85以上' ,(SELECT COUNT()FROM sc a WHERE a.score<85 AND a.C=b.c AND c.c=a.C AND a.score>70 AND a.C='01') '[70_85]' ,(SELECT COUNT()FROM sc a WHERE a.score>70 AND a.C=b.c AND c.c=a.C AND a.score>60 AND a.C='01') '[60_70]' ,(SELECT COUNT()FROM sc a WHERE a.score<60 AND a.C=b.c AND c.c=a.C AND a.C='01') '60一下' ,(SELECT COUNT()FROM sc a WHERE a.score>85 AND a.C=b.c AND c.c=a.C AND a.C='01')/(SELECT COUNT()FROM sc WHERE c='01'AND C=b.c AND c.c=c) '85以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score<85 AND a.C=b.c AND c.c=a.C AND a.score>70 AND a.C='01')/(SELECT COUNT()FROM sc WHERE c='01'AND C=b.c AND c.c=c) '[70_85]以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score>70 AND a.C=b.c AND c.c=a.C AND a.score>60 AND a.C='01')/(SELECT COUNT()FROM sc WHERE c='01'AND C=b.c AND c.c=c)'[60_70]以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score<60 AND a.C=b.c AND c.c=a.C AND a.C='01')/(SELECT COUNT()FROM sc WHERE c='01'AND C=b.c AND c.c=c)'60以上比率' FROM sc b ,course c WHERE b.c=c.c AND c.c='01' UNION ALL SELECT c.Cname ,(SELECT COUNT()FROM sc a WHERE a.score>85 AND a.C=b.c AND c.c=a.C AND a.C='02') '85以上' ,(SELECT COUNT()FROM sc a WHERE a.score<85 AND a.C=b.c AND c.c=a.C AND a.score>70 AND a.C='02') '[70_85]' ,(SELECT COUNT()FROM sc a WHERE a.score>70 AND a.C=b.c AND c.c=a.C AND a.score>60 AND a.C='02') '[60_70]' ,(SELECT COUNT()FROM sc a WHERE a.score<60 AND a.C=b.c AND c.c=a.C AND a.C='02') '60一下' ,(SELECT COUNT()FROM sc a WHERE a.score>85 AND a.C=b.c AND c.c=a.C AND a.C='02')/(SELECT COUNT()FROM sc WHERE c='02'AND C=b.c AND c.c=c) '85以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score<85 AND a.C=b.c AND c.c=a.C AND a.score>70 AND a.C='02')/(SELECT COUNT()FROM sc WHERE c='02'AND C=b.c AND c.c=c)'[70_85]以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score>70 AND a.C=b.c AND c.c=a.C AND a.score>60 AND a.C='02')/(SELECT COUNT()FROM sc WHERE c='02'AND C=b.c AND c.c=c)'[60_70]以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score<60 AND a.C=b.c AND c.c=a.C AND a.C='02')/(SELECT COUNT()FROM sc WHERE c='02'AND C=b.c AND c.c=c)'60以上比率' FROM sc b ,course c WHERE b.c=c.c AND c.c='02' UNION ALL SELECT c.Cname ,(SELECT COUNT()FROM sc a WHERE a.score>85 AND a.C=b.c AND c.c=a.C AND a.C='03') '85以上' ,(SELECT COUNT()FROM sc a WHERE a.score<85 AND a.C=b.c AND c.c=a.C AND a.score>70 AND a.C='03') '[70_85]' ,(SELECT COUNT()FROM sc a WHERE a.score>70 AND a.C=b.c AND c.c=a.C AND a.score>60 AND a.C='03') '[60_70]' ,(SELECT COUNT()FROM sc a WHERE a.score<60 AND a.C=b.c AND c.c=a.C AND a.C='03') '60一下' ,(SELECT COUNT()FROM sc a WHERE a.score>85 AND a.C=b.c AND c.c=a.C AND a.C='03')/(SELECT COUNT()FROM sc WHERE c='03'AND C=b.c AND c.c=c) '85以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score<85 AND a.C=b.c AND c.c=a.C AND a.score>70 AND a.C='03')/(SELECT COUNT()FROM sc WHERE c='03'AND C=b.c AND c.c=c)'[70_85]以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score>70 AND a.C=b.c AND c.c=a.C AND a.score>60 AND a.C='03')/(SELECT COUNT()FROM sc WHERE c='03'AND C=b.c AND c.c=c)'[60_70]以上比率' ,(SELECT COUNT()FROM sc a WHERE a.score<60 AND a.C=b.c AND c.c=a.C AND a.C='01')/(SELECT COUNT()FROM sc WHERE c='03'AND C=b.c AND c.c=c)'60以上比率' FROM sc b ,course c WHERE b.c=c.c AND c.c='03') a

--24、查询学生平均成绩及其名次

SELECT a.s ,a.avgscore ,@rownum:=@rownum +1 AS rownum FROM (SELECT s ,AVG(score) avgscore FROM sc GROUP BY s ORDER BY avgscore DESC ) a ,(SELECT @rownum:=0)r

--25、查询各科成绩前三名的记录

SELECT a.* ,b.* FROM (SELECT b.s ,b.C ,b.score ,(SELECT COUNT() FROM sc a WHERE a.c='01'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='01' HAVING mc BETWEEN 1 AND 3 UNION ALL SELECT b.s ,b.C ,b.score ,(SELECT COUNT() FROM sc a WHERE a.c='02'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='02' HAVING mc BETWEEN 1 AND 3 UNION ALL SELECT b.s ,b.C ,b.score ,(SELECT COUNT(*) FROM sc a WHERE a.c='03'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='03' HAVING mc BETWEEN 1 AND 3 ) a ,student b WHERE a.s =b.s

--26、查询每门课程被选修的学生数

SELECT a.Cname ,COUNT(b.c) FROM sc b,course a WHERE a.c =b.c GROUP BY b.c

--27、查询出只有两门课程的全部学生的学号和姓名

SELECT b.S ,b.Sname ,a.countc FROM (SELECT s ,COUNT(c) countc FROM sc GROUP BY s HAVING countc =2) a ,student b WHERE a.s=b.s

--28、查询男生、女生人数

select s.Ssex,COUNT()from student s where s.Ssex='男' UNION select s.Ssex,COUNT()from student s where s.Ssex='女'

--29、查询名字中含有"风"字的学生信息

SELECT * ,count(*) FROM student WHERE Sname rLIKE '风'

--30、查询同名同性学生名单，并统计同名人数

SELECT s.Sname ,s.Ssex ,COUNT(*) countnum from student s GROUP BY s.Sname,s.Ssex HAVING countnum>=2

--31、查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)

SELECT * FROM student WHERE Sage LIKE '1990%'

--32、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号

SELECT a.Cname ,AVG(sc.score) avgscore FROM sc ,course a WHERE sc.C =a.C GROUP BY sc.C ORDER BY avgscore DESC

--33、查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩

SELECT * FROM (SELECT a.Sname ,a.S ,AVG(sc.score) avgscore FROM sc ,student a WHERE sc.s =a.s GROUP BY sc.s ORDER BY avgscore DESC ) a WHERE a.avgscore>85

--34、查询课程名称为"数学"，且分数低于60的学生姓名和分数

SELECT * FROM sc a,course b WHERE a.c =b.c AND b.Cname='数学' AND a.score>60

--35、查询所有学生的课程及分数情况；

SELECT * FROM student a ,course b ,sc c WHERE a.S=c.S AND b.C =c.C

--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；

SELECT b.Sname ,c.Cname ,a.score FROM sc a, student b,course c WHERE a.score>70 AND a.C =c.C AND a.S =b.S

--37、查询不及格的课程

SELECT b.Sname ,c.Cname ,a.score FROM sc a, student b,course c WHERE a.score<60 AND a.C =c.C AND a.S =b.S

--38、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；

SELECT c.S ,c.Sname ,a.Cname ,b.score FROM course a ,sc b ,student c WHERE a.C =b.C AND b.score>=80 AND c.S =b.S AND a.C='01'

--39、求每门课程的学生人数

SELECT b.Cname ,COUNT(a.c) FROM sc a ,course b WHERE b.c=a.C GROUP BY a.C

--40、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩

SELECT b.* ,MAX(c.score) FROM teacher a,student b ,sc c ,course d WHERE a.T =d.T AND d.C =c.C AND c.S =b.S AND a.Tname ='张三'

--41、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

SELECT c.* FROM sc c GROUP BY c.C,c.score HAVING COUNT(*)>1;

--42、查询每门功成绩最好的前两名

SELECT a.* ,b.* FROM (SELECT b.s ,b.C ,b.score ,(SELECT COUNT() FROM sc a WHERE a.c='01'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='01' HAVING mc BETWEEN 1 AND 2 UNION ALL SELECT b.s ,b.C ,b.score ,(SELECT COUNT() FROM sc a WHERE a.c='02'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='02' HAVING mc BETWEEN 1 AND 2 UNION ALL SELECT b.s ,b.C ,b.score ,(SELECT COUNT(*) FROM sc a WHERE a.c='03'AND a.score>b.score)+1 mc FROM sc b WHERE b.c='03' HAVING mc BETWEEN 1 AND 2 ) a ,student b WHERE a.s =b.s

--43、统计每门课程的学生选修人数（超过5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

SELECT b.C ,b.Cname ,COUNT(a.C) countc FROM sc a,course b WHERE a.c=b.C GROUP BY a.C HAVING countc>5 ORDER BY countc DESC

--44、检索至少选修两门课程的学生学号

SELECT sc.S ,COUNT(sc.C) countc FROM sc GROUP BY sc.S HAVING countc >=2

--45、查询选修了全部课程的学生信息

SELECT a.* ,COUNT(sc.C) countc FROM sc ,student a WHERE sc.S =a.S GROUP BY sc.S HAVING countc =3

--46、查询各学生的年龄

SELECT s.s, s.sname, EXTRACT(YEAR FROM NOW())-EXTRACT(YEAR FROM s.sage) 年龄 FROM student s

--47、查询本周过生日的学生

SELECT s.S ,s.Sname ,s.Sage FROM student s WHERE YEARWEEK(DATE_FORMAT(s.Sage,'%Y-%m-%d')) =YEARWEEK(NOW())

--48、查询下周过生日的学生

SELECT s.S ,s.Sname ,s.Sage FROM student s WHERE YEARWEEK(DATE_FORMAT(s.Sage,'%Y-%m-%d')) =YEARWEEK(NOW())+1

--49、查询本月过生日的学生

SELECT s.S ,s.Sname ,s.Sage FROM student s WHERE MONTH(DATE_FORMAT(s.Sage,'%Y-%m-%d')) =MONTH(NOW())

--50、查询下月过生日的学生

SELECT s.S ,s.Sname ,s.Sage FROM student s WHERE MONTH(DATE_FORMAT(s.Sage,'%Y-%m-%d')) =MONTH(NOW())+1