2020-08-15 我要开始记录和学习了！

刷sql45和记录

CREATE TABLE students
(sno VARCHAR(3) NOT NULL, 
sname VARCHAR(4) NOT NULL,
ssex VARCHAR(2) NOT NULL, 
sbirthday DATETIME,
class VARCHAR(5))

CREATE TABLE courses
(cno VARCHAR(5) NOT NULL, 
cname VARCHAR(10) NOT NULL, 
tno VARCHAR(10) NOT NULL)

CREATE TABLE scores 
(sno VARCHAR(3) NOT NULL, 
cno VARCHAR(5) NOT NULL, 
degree NUMERIC(10, 1) NOT NULL) 

CREATE TABLE teachers 
(tno VARCHAR(3) NOT NULL, 
tname VARCHAR(4) NOT NULL, tsex VARCHAR(2) NOT NULL, 
tbirthday DATETIME NOT NULL, prof VARCHAR(6), 
depart VARCHAR(10) NOT NULL)

INSERT INTO STUDENTS (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (108 ,'曾华' ,'男' ,'1977-09-01',95033);
INSERT INTO STUDENTS (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (105 ,'匡明' ,'男' ,'1975-10-02',95031);
INSERT INTO STUDENTS (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (107 ,'王丽' ,'女' ,'1976-01-23',95033);
INSERT INTO STUDENTS (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (101 ,'李军' ,'男' ,'1976-02-20',95033);
INSERT INTO STUDENTS (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (109 ,'王芳' ,'女' ,'1975-02-10',95031);
INSERT INTO STUDENTS (SNO,SNAME,SSEX,SBIRTHDAY,CLASS) VALUES (103 ,'陆君' ,'男' ,'1974-06-03',95031);

INSERT INTO COURSES(CNO,CNAME,TNO)VALUES ('3-105' ,'计算机导论',825);
INSERT INTO COURSES(CNO,CNAME,TNO)VALUES ('3-245' ,'操作系统' ,804);
INSERT INTO COURSES(CNO,CNAME,TNO)VALUES ('6-166' ,'数据电路' ,856);
INSERT INTO COURSES(CNO,CNAME,TNO)VALUES ('9-888' ,'高等数学' ,100);

INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (103,'3-245',86);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (105,'3-245',75);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (109,'3-245',68);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (103,'3-105',92);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (105,'3-105',88);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (109,'3-105',76);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (101,'3-105',64);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (107,'3-105',91);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (108,'3-105',78);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (101,'6-166',85);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (107,'6-106',79);
INSERT INTO SCORES(SNO,CNO,DEGREE)VALUES (108,'6-166',81);

INSERT INTO TEACHERS(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART) VALUES (804,'李诚','男','1958-12-02','副教授','计算机系');
INSERT INTO TEACHERS(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART) VALUES (856,'张旭','男','1969-03-12','讲师','电子工程系');
INSERT INTO TEACHERS(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART) VALUES (825,'王萍','女','1972-05-05','助教','计算机系');
INSERT INTO TEACHERS(TNO,TNAME,TSEX,TBIRTHDAY,PROF,DEPART) VALUES (831,'刘冰','女','1977-08-14','助教','电子工程系');

题目：

#1、 查询Student表中的所有记录的Sname、Ssex和Class列。students
select sname,ssex,class from students;

#2、 查询教师所有的单位即不重复的Depart列。
select distinct depart from teachers;

#3、 查询Student表的所有记录。
select * from students;

#4、 查询Score表中成绩在60到80之间的所有记录。
select * from scores where degree between 60 and 80;

#5、 查询Score表中成绩为85，86或88的记录。
select * from scores 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 students where class='95031' or ssex='女';

#7、 以Class降序查询Student表的所有记录。
select * from students order by class desc;

#8、 以Cno升序、Degree降序查询Score表的所有记录。
select * FROM SCORES ORDER BY Cno,degree DESC;

#9、 查询“95031”班的学生人数。 
SELECT COUNT(1) FROM students where class="95031";
#select count(distinct sno) from students where class='95031'

#10、查询Score表中的最高分的学生学号和课程号。
select * from scores where degree = (select max(degree) from scores);

#11、查询'3-105'号课程的平均分。
select avg(degree) from scores where cno='3-105';

#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。
select cno,avg(degree) from scores 
group by cno having count(sno)>5
where cno like '3%';
/*
select cno,avg(degree) from scores 
where cno like '3%'
group by cno having count(cno)>5
;
*/

#13、查询最低分大于70，最高分小于90的Sno列。
#不会，以下为答案
#select sno from scores group by sno having 
#min(degree) >70 and max(degree) <90


#14、查询所有学生的Sname、Cno和Degree列。
select s.sname,scores.cno,scores.degree 
from STUDENTS s
JOIN scores
on s.sno=scores.sno
order by s.sno;

#15、查询所有学生的Sno、Cname和Degree列。
select s.sno,c.cname,scores.degree
from students s join scores 
on s.sno=scores.sno
join courses c
on scores.cno=c.cno
order by s.sno;


#16、查询所有学生的Sname、Cname和Degree列。
select s.sname,c.cname,scores.degree
from students s join scores 
on s.sno=scores.sno
join courses c
on scores.cno=c.cno
order by s.sno;


#17、查询“95033”班所选课程的平均分。
select s.class,avg(scores.degree) from students s
join scores 
on s.sno=scores.sno
group by s.class
having s.class="95033";
#以下为答案：
select avg(degree) from scores where 
sno in (select sno from students where class='95033');

#18、假设使用如下命令建立了一个grade表：
create table grade(low   number(3,0),upp number(3),rank char(1));
#为什么上面的会报错？

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’);
commit;

#18、现查询所有同学的Sno、Cno和rank列。
#不会，以下是答案
SELECT Sno,Cno,rank_
FROM Scores INNER JOIN grade
ON(Scores.Degree>=grade.low AND Scores.Degree<=grade.upp)
ORDER BY Sno;

#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。
#第一次做忘了 on
select *
from students 
join scores
on students.sno=scores.sno
where scores.cno='3-105'
and scores.degree>(
select degree from scores
where sno="109" and cno='3-105');

#答案
select *from students where sno in
(select sno from scores where  cno='3-105' and  
degree>(select scores.degree from scores 
where sno='109' and cno='3-105'));

#注意是要学生的资料

#20、查询score中选学一门以上课程的同学中分数为非最高分成绩的记录。

select * from scores join 
(select sno,count(cno) from scores 
group by sno
having count(cno)>1) as t
on scores.sno=t.sno
where scores.degree not in (
select max(degree) from scores);

SELECT *
FROM Scores
GROUP BY Sno
HAVING COUNT(cno)>1 AND Degree != MAX(Degree);

#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。
#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。

#这个跟19有什么区别吗。。。
#19应该是学生的记录，这里是成绩的记录？
select * from scores 
where cno="3-105"
and degree >(
select degree from scores
where cno="3-105" and sno="109");


#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 students 
where year(sbirthday)=(select year(sbirthday) from students where sno="108");

#以下为答案验证
SELECT s1.Sno,s1.Sname,s1.Sbirthday
FROM Students AS s1 INNER JOIN Students AS s2
ON(YEAR(s1.Sbirthday)=YEAR(s2.Sbirthday))
WHERE s2.Sno='108';

#23、查询“张旭“教师任课的学生成绩。

select * from scores where
cno in 
(select cno from teachers join courses
on teachers.tno=courses.tno
where teachers.tname='张旭');

select sno,degree from scores where cno = 
(select cno from courses where tno =
(select tno from teachers 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。

select teachers.tname,count(distinct scores.sno)
from teachers 
join courses
on teachers.tno=courses.tno
join scores
on courses.cno=scores.cno
group by teachers.tname
having count(distinct scores.sno)>5;

#25、查询95033班和95031班全体学生的记录。

select * from students where class in (95033,95031);


#26、查询存在有85分以上成绩的课程Cno.

select courses.cno from courses where courses.cno in 
(select cno from scores
where degree > 85);

#答案
select cno from scores group by cno having MAX(degree)>85;


#27、查询出“计算机系“教师所教课程的成绩表。

select * from scores join courses
on scores.cno=courses.cno
join teachers 
on teachers.tno=courses.tno
where teachers.depart='计算机系';

#答案
select sc.DEGREE
from scores sc INNER JOIN teachers t INNER JOIN courses c
on(t.TNO=c.TNO and c.CNO=sc.CNO)
where t.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。

#不会
select te.TNAME,te.PROF
from teachers te , teachers tea
where te.depart=tea.depart and te.prof <>tea.prof;

select distinct te.TNAME,te.PROF
from teachers te , teachers tea
where te.depart=tea.depart and te.prof <>tea.prof;

#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。
 
#不会
select cno,sno,degree from Scores where Cno='3-105' and 
degree >(select max(degree) from Scores 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.
#不会，跟上面一题有不同吗？
select Cno,Sno,degree from Scores a where Cno='3-105' and Degree >
(select degree from Scores b where Cno='3-245' and a.sno=b.sno);


#31、查询所有教师和同学的name、sex和birthday.
select s.sname as name,s.ssex as sex,s.sbirthday as birthday
from students s
union
select t.tname,tsex,tbirthday
from teachers t;

#32、查询所有“女”教师和“女”同学的name、sex和birthday.
select s.sname as name,s.ssex as sex,s.sbirthday as birthday
from students s 
where s.ssex= "女"
union
select t.tname,tsex,tbirthday
from teachers t
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 s.sno,s.cno,s.degree,avgt.avgScoure from scores s
join 
(select s.cno,avg(s.degree) as avgScoure from scores s
group by s.cno) avgt
on s.cno=avgt.cno
where s.degree < avgt.avgScoure;

select * from Scores a where degree <
(select AVG(degree) from Scores b group by Cno having a.cno=b.cno);


#34、查询所有任课教师的Tname和Depart.
select tname,depart from teachers
join courses
on teachers.tno=courses.tno;

select distinct tname,depart from Scores a join Courses b on a.Cno=b.Cno join 
Teachers c on b.Tno=c.Tno where a.Cno in (b.cno);


#35  查询所有未讲课的教师的Tname和Depart. 
select tname,depart from teachers
where tno not in (
select tno from courses);

select Tname,depart from Teachers where Tno not in 
(select c.tno from Scores a join Courses b on a.Cno=b.Cno join 
Teachers c on b.Tno=c.tno where a.Cno in (b.cno) );

#36、查询至少有2名男生的班号。
select scores.cno,count(scores.sno) from scores 
join students 
on scores.sno=students.sno
where students.ssex="男"
group by scores.cno having count(scores.sno)>2;
#上面我做的是错的，应该看students表
select class from students where Ssex='男' group by class having count(class)>=2 

#37、查询Student表中不姓“王”的同学记录。

select * from students where sname not like '王%';

#38、查询Student表中每个学生的姓名和年龄。

select sname, year(today())-year(sbirthday) as age from students;
#上面是第一次做错的，sql没有today()

select sname, year(now())-year(sbirthday) as age from students;

#39、查询Student表中最大和最小的Sbirthday日期值。
select max(sbirthday),min(sbirthday) from students;

#40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
#注意年龄从达到小，=出生日期从小到大
select * from students order by class desc, sbirthday;

#41、查询“男”教师及其所上的课程。
select cno,cname from courses 
join teachers on courses.tno=teachers.tno
where teachers.tsex='男'; 

#42、查询最高分同学的Sno、Cno和Degree列。
#直接像下面这样用是错误的
select sno,cno,degree from scores 
where degree=max(degree);
#这样也不行
select sno,cno,max(degree) from scores 
group by sno,cno;
#这样也不行？？？？
select sno,cno,degree from scores 
where degree in 
(select max(degree) from scores);

select * from scores a where a.degree=(
select MAX(b.degree) from scores b group by b.cno having a.cno=b.cno);

#43、查询和“李军”同性别的所有同学的Sname.
select sname from students 
where ssex=(select ssex from students where sname='李军');

#44、查询和“李军”同性别并同班的同学Sname.

select sname from students
where ssex in(select ssex from students where sname="李军")
and class in (select class from students 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

select * from scores
join courses on
scores.cno=courses.cno
join students
on scores.sno=students.sno
where courses.cname='计算机导论' and students.ssex="男";