增刪改查的45道題

標籤：

1、查詢Student表中的所有記錄的Sname、Ssex和Class列。
select Sname,Ssex,Class from student

2、查詢教師所有的單位即不重複的Depart列。
select distinct depart from teacher #去重用distinct

3、查詢Student表的所有記錄。
select * from student #查詢所有的用*

4、查詢Score表中成績在60到80之間的所有記錄。
select * from score where degree between 60 and 80
or select * from score where degree >=60 && degree <=80 # &&可以用and

5、查詢Score表中成績為85，86或88的記錄。
select * from score where degree =85 ||degree =86 ||degree =88
or select * from score where degree in (85,86,88)

6、查詢Student表中“95031”班或性別為“女”的同學記錄。
select * from student where class =‘95031‘or ssex=‘女‘ #or可以用||

7、以Class降序查詢Student表的所有記錄。
select * from student order by Class desc #排序order by 降序desc 升序asc

8、以Cno升序、Degree降序查詢Score表的所有記錄。
select * from score order by degree desc,cno asc

9、查詢“95031”班的學生人數。
select count(*) from student where class =‘95031‘

10、查詢Score表中的最高分的學生學號和課程號。（子查詢或者排序）
方法一排序：select sno,cno from score order by degree desc limit 0,1 #從0索引取1個
方法二：select sno,cno from score where degree =(select max(degree) from score)
查詢語句查詢出一個或者一列結果，可以作為其他查詢語句的參數來使用，這就是子查詢，也就是查詢嵌套

11、查詢每門課的平均成績。
select avg(degree),cno from score group by cno

12、查詢Score表中至少有5名學生選修的並以3開頭的課程的平均分數。
思路：查詢以3開頭的課程的平均分數
select cno, avg(degree) from score where cno like ‘3%‘ group by cno
查詢至少有5名學生選修的cno
select cno from score group by cno having count(*)>=5
綜合：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、查詢分數大於70，小於90的Sno列。
select sno from score where degree >70 and degree<90

14、查詢所有學生的Sname、Cno和Degree列 #是student和score的結合
方法一：select sname,cno,degree from student,score where student.sno = score.sno #不建議
方法二：select sname,cno,degree from student join score on student.sno = score.sno #常規的做法
方法三：select(select sname from student where student.sno = score.sno),cno,degree from score #子查詢比較麻煩

15、查詢所有學生的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、查詢所有學生的Sname、Cname和Degree列。
select sname,cname,degree from student,course,score where score.cno = course.cno
and student.sno =score.sno

17、查詢“95033”班學生的平均分。
自己的：select avg(degree),cno from score where sno in
(select sno from student where class =‘95033‘)group by cno #選修的課程不一樣
老師的：select avg(degree) from score where sno in
(select sno from student where class =‘95033‘) #所以課程的平均

18、 假設使用如下命令建立了一個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’)
現查詢所有同學的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是將沒有用的排序留下的是所在分數範圍內的

19、 查詢選修“3-105”課程的成績高於“109”號同學成績的所有同學的記錄。
題目理解：選修3-105 並且成績大於109號選修3-105的
select * from score where cno =‘3-105‘and degree >
(select degree from score where sno =‘109‘ and cno =‘3-105‘ )

20、查詢score中選學多門課程的同學中分數為非最高分成績的記錄。
題目理解：這個課程的非最高，有歧義看自己的理解
思路：1）查詢成績為非最高分
select * from score a where degree <
(select max(degree) from score b where b.cno = a.cno)
2）查詢選修多門的同學的sno
select sno from score where sno in
(select sno from score group by sno having count(*)>1)
匯總後：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、查詢成績高於學號為“109”、課程號為“3-105”的成績的所有記錄。
select * from score where degree >
(select degree from score where sno =‘109‘ and cno =‘3-105‘ )

22、查詢和學號為108的同學同年出生的所有學生的Sno、Sname和Sbirthday列。
select sno,sname,sbirthday from student
where YEAR(sbirthday) = (select YEAR(sbirthday) from student where sno =‘108‘) #取年的函數YEAR(sbirthday)

23、查詢“張旭“教師任課的學產生績。
思路：主查詢是學生的成績，以cno為主線；
Teacher 中張旭的Tno，和course中的Tno相等時的Cno #從teacher到course再到score
select * from score where cno in
(select cno from course where tno =
(select tno from teacher where tname =‘張旭‘))

24、查詢選修某課程的同學人數多於5人的教師姓名。 #從score到course再到teacher
思路：1)select Cno from score group by Cno having count(*)>5 #在score表中查詢選修課程人數大於5的
匯總：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、查詢95033班和95031班全體學生的記錄。
select * from student where class in (‘95033‘,‘95031‘)

26、查詢存在有85分以上成績的課程Cno.
select distinct cno from score where degree >85

27、查詢出“電腦系“教師所教課程的成績表。 #從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 =‘電腦系‘) )

28、查詢“電腦系”與“電子工程系“不同職稱的教師的Tname和Prof。
理解不同：我的想法是：以電腦係為准，查詢那個與電子工程系不同的 #只有電腦系
select tname,prof from teacher where depart =‘電腦系‘and
prof not in (select prof from teacher where depart =‘電子工程系‘)
老師的想法是：查出兩個系中職稱不同的 #包含兩個系的內容
select * from teacher where prof not in
(select prof from teacher where depart =‘電腦系‘and
prof in (select prof from teacher where depart =‘電子工程系‘))
另一種方法：select * from Teacher where prof in
(select prof from Teacher where Depart =‘電腦系‘ and prof
not in (select prof from Teacher where Depart = ‘電子工程系‘))
union
select * from Teacher where prof in
(select prof from Teacher where Depart =‘電子工程系‘ and prof
not in (select prof from Teacher where Depart = ‘電腦系‘))
和我的想法一樣不過得union聯合

29、查詢選修編號為“3-105“課程且成績至少高於選修編號為“3-245”
的同學的Cno、Sno和Degree,並按Degree從高到低次序排序。 #都是按sno相同時來
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、查詢選修編號為“3-105”且成績高於選修編號為“3-245”課程的同學的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，與上面對比any 是至少

31、 查詢所有教師和同學的name、sex和birthday.
select sname,ssex,sbirthday from student
union select tname,tsex,tbirthday from teacher

32、查詢所有“女”教師和“女”同學的name、sex和birthday.
select sname,ssex,sbirthday from student where ssex =‘女‘ union
select tname,tsex,tbirthday from teacher where tsex =‘女‘

33、 查詢成績比該課程平均成績低的同學的成績表。
select * from score a where degree <
(select avg(degree) from score b where a.cno =b.cno )

34、 查詢所有任課教師的Tname和Depart. #score表中的 從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 、查詢所有未講課的教師的Tname和Depart.
select tname,depart from teacher where tno not in
(select tno from course where cno in (select cno from score ))

36、查詢至少有2名男生的班號。
select class from student where ssex =‘男‘ and group by class having count(*)>1

37、查詢Student表中不姓“王”的同學記錄。
select * from student where sname not like ‘王%‘

38、查詢Student表中每個學生的姓名和年齡。
select sname,YEAR(now())-YEAR(sbirthday)from student

39、查詢Student表中最大和最小的Sbirthday日期值。
select max(sbirthday),min(sbirthday)from student

40、以班號和年齡從大到小的順序查詢Student表中的全部記錄。
select class,sbirthday from student order by class desc,sbirthday asc #asc可以省略

41、查詢“男”教師及其所上的課程。 #從teacher到course
select cname from course where tno in
(select tno from teacher where tsex =‘男‘) #只是查出教的課程
自己的：select tname,cname from teacher,course where teacher.tno = course.tno
and tsex =‘男‘

42、查詢最高分同學的Sno、Cno和Degree列。
排序：select sno,cno,degree from score order by degree desc limit 0,1
子查詢：select sno,cno,degree from score where degree = (select max(degree)from score)

43、查詢和“李軍”同性別的所有同學的Sname.
select sname from student where ssex =(select ssex from student where sname =‘李軍‘)

44、查詢和“李軍”同性別並同班的同學Sname.
select sname from student where ssex =
(select ssex from student where sname =‘李軍‘)and class =
(select class from student where sname=‘李軍‘)

45、查詢所有選修“電腦導論”課程的“男”同學的成績表。 #從course到score,從studen到score
select * from score where cno in(select cno from course where cname =‘電腦導論‘)
and sno in(select sno from student where ssex =‘男‘)

增刪改查的45道題