1、查询Student表中的所有记录的Sname、Ssex和Class列。
select Sname,Ssex,Class from student
2、查询教师所有的单位即不重复的Depart列。
select distinct depart from teacher #去重用distinct
3、查询Student表的所有记录。
select * from student #查询所有的用*
4、查询Score表中成绩在60到80之间的所有记录。
select * from score where degree between 60 and 80
or select * from score where degree >=60 && degree <=80 # &&可以用and
5、查询Score表中成绩为85，86或88的记录。
select * from score where degree =85 ||degree =86 ||degree =88
or select * from score where degree in (85,86,88)
6、查询Student表中“95031”班或性别为“女”的同学记录。
select * from student where class =‘95031‘or ssex=‘女‘ #or可以用||
7、以Class降序查询Student表的所有记录。
select * from student order by Class desc #排序order by 降序desc 升序asc
8、以Cno升序、Degree降序查询Score表的所有记录。
select * from score order by degree desc,cno asc
9、查询“95031”班的学生人数。
select count(*) from student where class =‘95031‘
10、查询Score表中的最高分的学生学号和课程号。（子查询或者排序）
方法一排序：select sno,cno from score order by degree desc limit 0,1 #从0索引取1个
方法二：select sno,cno from score where degree =(select max(degree) from score)
查询语句查询出一个或者一列结果，可以作为其他查询语句的参数来使用，这就是子查询，也就是查询嵌套
11、查询每门课的平均成绩。
select avg(degree),cno from score group by cno
12、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。
思路：查询以3开头的课程的平均分数
select cno, avg(degree) from score where cno like ‘3%‘ group by cno
查询至少有5名学生选修的cno
select cno from score group by cno having count(*)>=5
综合：select avg(degree),cno from score where cno in
(select cno from score where cno like ‘3%‘ group by cno having count(*)>=5)group by cno
13、查询分数大于70，小于90的Sno列。
select sno from score where degree >70 and degree<90
14、查询所有学生的Sname、Cno和Degree列 #是student和score的结合
方法一：select sname,cno,degree from student,score where student.sno = score.sno #不建议
方法二：select sname,cno,degree from student join score on student.sno = score.sno #常规的做法
方法三：select(select sname from student where student.sno = score.sno),cno,degree from score #子查询比较麻烦
15、查询所有学生的Sno、Cname和Degree列。
方法一：select sno,cname,degree from score,course where score.cno = course.cno
方法二：select sno,cname,degree from score join course on score.cno = course.cno
16、查询所有学生的Sname、Cname和Degree列。
select sname,cname,degree from student,course,score where score.cno = course.cno
and student.sno =score.sno
17、查询“95033”班学生的平均分。
自己的：select avg(degree),cno from score where sno in
(select sno from student where class =‘95033‘)group by cno #选修的课程不一样
老师的：select avg(degree) from score where sno in
(select sno from student where class =‘95033‘) #所以课程的平均
18、 假设使用如下命令建立了一个grade表：
create table grade(low int(3),upp int(3),rank char(1))
insert into grade values(90,100,’A’)
insert into grade values(80,89,’B’)
insert into grade values(70,79,’C’)
insert into grade values(60,69,’D’)
insert into grade values(0,59,’E’)
现查询所有同学的Sno、Cno和rank列。
select sno,cno,rank from score,grade where degree between low and upp
select sno,cno,rank from score join grade on degree between low and upp
#between low and upp是将没有用的排序留下的是所在分数范围内的
19、 查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。
题目理解：选修3-105 并且成绩大于109号选修3-105的
select * from score where cno =‘3-105‘and degree >
(select degree from score where sno =‘109‘ and cno =‘3-105‘ )
20、查询score中选学多门课程的同学中分数为非最高分成绩的记录。
题目理解：这个课程的非最高，有歧义看自己的理解
思路：1）查询成绩为非最高分
select * from score a where degree <
(select max(degree) from score b where b.cno = a.cno)
2）查询选修多门的同学的sno
select sno from score where sno in
(select sno from score group by sno having count(*)>1)
汇总后：select * from score a where degree<
(select max(degree)from score b where b.cno = a.cno)
and sno in (select sno from score group by sno having count(*)>1)
21、查询成绩高于学号为“109”、课程号为“3-105”的成绩的所有记录。
select * from score where degree >
(select degree from score where sno =‘109‘ and cno =‘3-105‘ )
22、查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
select sno,sname,sbirthday from student
where YEAR(sbirthday) = (select YEAR(sbirthday) from student where sno =‘108‘) #取年的函数YEAR(sbirthday)
23、查询“张旭“教师任课的学生成绩。
思路：主查询是学生的成绩，以cno为主线；
Teacher 中张旭的Tno，和course中的Tno相等时的Cno #从teacher到course再到score
select * from score where cno in
(select cno from course where tno =
(select tno from teacher where tname =‘张旭‘))
24、查询选修某课程的同学人数多于5人的教师姓名。 #从score到course再到teacher
思路：1)select Cno from score group by Cno having count(*)>5 #在score表中查询选修课程人数大于5的
汇总：select tname from teacher where tno in
(select tno from course where cno in
(select cno from score group by cno having count(*)>5))
25、查询95033班和95031班全体学生的记录。
select * from student where class in (‘95033‘,‘95031‘)
26、查询存在有85分以上成绩的课程Cno.
select distinct cno from score where degree >85
27、查询出“计算机系“教师所教课程的成绩表。 #从teacher到course再到score
select * from score where cno in
(select cno from course where tno in
(select tno from teacher where depart =‘计算机系‘) )
28、查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
理解不同：我的想法是：以计算机系为准，查询那个与电子工程系不同的 #只有计算机系
select tname,prof from teacher where depart =‘计算机系‘and
prof not in (select prof from teacher where depart =‘电子工程系‘)
老师的想法是：查出两个系中职称不同的 #包含两个系的内容
select * from teacher where prof not in
(select prof from teacher where depart =‘计算机系‘and
prof in (select prof from teacher where depart =‘电子工程系‘))
另一种方法：select * from Teacher where prof in
(select prof from Teacher where Depart =‘计算机系‘ and prof
not in (select prof from Teacher where Depart = ‘电子工程系‘))
union
select * from Teacher where prof in
(select prof from Teacher where Depart =‘电子工程系‘ and prof
not in (select prof from Teacher where Depart = ‘计算机系‘))
和我的想法一样不过得union联合
29、查询选修编号为“3-105“课程且成绩至少高于选修编号为“3-245”
的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。 #都是按sno相同时来
select cno,sno,degree from score where cno =‘3-105‘and degree >
any (select degree from score where cno =‘3-245‘)order by degree desc
30、查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的Cno、Sno和Degree.
select cno,sno,degree from score where cno =‘3-105‘and degree >
all (select degree from score where cno =‘3-245‘) #All 是所有的意思，与上面对比any 是至少
31、 查询所有教师和同学的name、sex和birthday.
select sname,ssex,sbirthday from student
union select tname,tsex,tbirthday from teacher
32、查询所有“女”教师和“女”同学的name、sex和birthday.
select sname,ssex,sbirthday from student where ssex =‘女‘ union
select tname,tsex,tbirthday from teacher where tsex =‘女‘
33、 查询成绩比该课程平均成绩低的同学的成绩表。
select * from score a where degree <
(select avg(degree) from score b where a.cno =b.cno )
34、 查询所有任课教师的Tname和Depart. #score表中的 从score到course再到teacher
select tname,depart from teacher where tno in
(select tno from course where cno in (select cno from score ))
35 、查询所有未讲课的教师的Tname和Depart.
select tname,depart from teacher where tno not in
(select tno from course where cno in (select cno from score ))
36、查询至少有2名男生的班号。
select class from student where ssex =‘男‘ and group by class having count(*)>1
37、查询Student表中不姓“王”的同学记录。
select * from student where sname not like ‘王%‘
38、查询Student表中每个学生的姓名和年龄。
select sname,YEAR(now())-YEAR(sbirthday)from student
39、查询Student表中最大和最小的Sbirthday日期值。
select max(sbirthday),min(sbirthday)from student
40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
select class,sbirthday from student order by class desc,sbirthday asc #asc可以省略
41、查询“男”教师及其所上的课程。 #从teacher到course
select cname from course where tno in
(select tno from teacher where tsex =‘男‘) #只是查出教的课程
自己的：select tname,cname from teacher,course where teacher.tno = course.tno
and tsex =‘男‘
42、查询最高分同学的Sno、Cno和Degree列。
排序：select sno,cno,degree from score order by degree desc limit 0,1
子查询：select sno,cno,degree from score where degree = (select max(degree)from score)
43、查询和“李军”同性别的所有同学的Sname.
select sname from student where ssex =(select ssex from student where sname =‘李军‘)
44、查询和“李军”同性别并同班的同学Sname.
select sname from student where ssex =
(select ssex from student where sname =‘李军‘)and class =
(select class from student where sname=‘李军‘)
45、查询所有选修“计算机导论”课程的“男”同学的成绩表。 #从course到score,从studen到score
select * from score where cno in(select cno from course where cname =‘计算机导论‘)
and sno in(select sno from student where ssex =‘男‘)