1、建表
學生表
student
學號,姓名,性別,出生,所在班級
create table student(
sno varchar(20) primary key,
sname varchar(20) not null,
ssex varchar(10) not null,
sbirthday datetime,
sclass varchar(20)
);
教師表
teacher
教師編號,教師名字,教師性別,出生,職稱,所在部門
create table teacher(
tno varchar(20) primary key,
tname varchar(20) not null,
tsex varchar(10) not null,
tbirthday datetime,
prof varchar(20) not null,
depart varchar(20) not null
);
課程表
course
課程號,課程名稱,教師編號
create table course(
cno varchar(20) primary key,
cname varchar(20) not null,
tno varchar(20) not null,
foreign key(tno) references teacher(tno)
);
成績表
score
學號,課程號,成績
create table score(
sno varchar(20) not null,
cno varchar(20) not null,
degree decimal,
foreign key(sno) references student(sno),
foreign key(cno) references course(cno),
primary key(sno, cno)
);
2、插入數據
添加學生信息
insert into student value('101','曾華','男','1977-09-01','95033');
insert into student value('102','匡明','男','1975-10-02','95031');
insert into student value('103','王麗','女','1977-01-23','95033');
insert into student value('104','李軍','男','1977-02-20','95033');
insert into student value('105','王芳','女','1977-02-10','95031');
insert into student value('106','陸軍','男','1977-06-03','95031');
insert into student value('107','李縮','男','1977-02-21','95033');
insert into student value('108','王解','女','1975-02-13','95031');
insert into student value('109','陸稍','男','1977-06-01','95031');
添加教師信息
insert into teacher value('834','李成','男','1958-12-01','副教授','計算機系');
insert into teacher value('856','張旭','男','1968-11-21','講師','電子工程系');
insert into teacher value('825','王品','女','1972-05-05','助教','計算機系');
insert into teacher value('831','劉冰','女','1977-08-14','助教','電子工程系');
添加課程表
insert into course value('3-245','計算機導論','825');
insert into course value('3-105','操作系統','834');
insert into course value('6-166','數字電路','856');
insert into course value('9-888','高等數學','831');
添加成績表
insert into score value('103','3-245','86');
insert into score value('105','3-245','75');
insert into score value('109','3-245','68');
insert into score value('103','3-105','92');
insert into score value('105','3-105','88');
insert into score value('109','3-105','76');
insert into score value('101','3-105','91');
insert into score value('102','3-105','78');
insert into score value('103','6-166','85');
insert into score value('105','6-166','79');
insert into score value('109','6-166','81');
3、表數據查看
學生
+-----+--------+------+---------------------+--------+
| sno | sname | ssex | sbirthday | sclass |
+-----+--------+------+---------------------+--------+
| 101 | 曾華 | 男 | 1977-09-01 00:00:00 | 95033 |
| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
| 103 | 王麗 | 女 | 1977-01-23 00:00:00 | 95033 |
| 104 | 李軍 | 男 | 1977-02-20 00:00:00 | 95033 |
| 105 | 王芳 | 女 | 1977-02-10 00:00:00 | 95031 |
| 106 | 陸軍 | 男 | 1977-06-03 00:00:00 | 95031 |
| 107 | 李縮 | 男 | 1977-02-21 00:00:00 | 95033 |
| 108 | 王解 | 女 | 1975-02-13 00:00:00 | 95031 |
| 109 | 陸稍 | 男 | 1977-06-01 00:00:00 | 95031 |
+-----+--------+------+---------------------+--------+
教師
+-----+--------+------+---------------------+-----------+-----------------+
| tno | tname | tsex | tbirthday | prof | depart |
+-----+--------+------+---------------------+-----------+-----------------+
| 825 | 王品 | 女 | 1972-05-05 00:00:00 | 助教 | 計算機系 |
| 831 | 劉冰 | 女 | 1977-08-14 00:00:00 | 助教 | 電子工程系 |
| 834 | 李成 | 男 | 1958-12-01 00:00:00 | 副教授 | 計算機系 |
| 856 | 張旭 | 男 | 1968-11-21 00:00:00 | 講師 | 電子工程系 |
+-----+--------+------+---------------------+-----------+-----------------+
課程
+-------+-----------------+-----+
| cno | cname | tno |
+-------+-----------------+-----+
| 3-105 | 操作系統 | 834 |
| 3-245 | 計算機導論 | 825 |
| 6-166 | 數字電路 | 856 |
| 9-888 | 高等數學 | 831 |
+-------+-----------------+-----+
成績
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 101 | 3-105 | 91 |
| 102 | 3-105 | 78 |
| 103 | 3-105 | 92 |
| 103 | 3-245 | 86 |
| 103 | 6-166 | 85 |
| 105 | 3-105 | 88 |
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
| 109 | 6-166 | 81 |
+-----+-------+--------+
4、查詢練習
1、查詢student表的所有記錄
select * from student;
2、查詢student表中的所有記錄的sname、ssex和sclass列
select sname, ssex, sclass from student;
3、查詢教師所有的單位即不重複的depart列
select distinct depart from teacher; //distinct排重
4、查詢score表中成績在60-80之間的所有記錄
select * from score where degree between 60 and 80;
select * from score where degree > 60 and degree < 80;
5、查詢score表中成績爲85,86或87的記錄
select * from score where degree in(85, 86, 87);
6、查詢student表中"95031"班，或性別爲'女'的同學記錄
select * from student where sclass='95031' or ssex='女';
7、以sclass降序查詢student表中的所有數據//desc降序 asc升序默認是升序的一般不會寫
select * from student order by sclass desc;
8、以cno升序、degree降序查詢score表中的所有記錄//遇到相同的就降序
select * from score order by cno asc ,degree desc;
9、查詢"95031"班級的人數
select count(*) from student where sclass = '95031';
10、查詢score表中最高分的學生學號和課程號。(子查詢或排序)
select sno, cno from score where degree = (select max(degree) from score);
select sno, cno, degree from score order by degree desc limit 0, 1;
如果按照分數排序，select的時候一定要把degree放進去，0表示從第一行開始數一行，如果是1, 2則表示從第二行開始數兩條
11、查詢每門課的平均成績
select * from course;
select avg(degree) from score where cno='3-105';
一門一門查詢
下面是寫在一句話中
select cno, avg(degree) from score group by cno;
12、查詢score表中至少有兩名學生選修的並以3開頭的課程的平均分數
select cno, avg(degree),count(*) from score group by cno having count(cno)>=2 and cno like '3%';
count(*)表示給出這個group的個數，此題也可以不加
13、查詢分數大於70小於90的sno列
select sno,degree from score where degree>70 and degree<90;
select sno,degree from score where degree between 70 and 90;
14、查詢所有學生的sname, cno和degree列
select sno, sname from student;
select sno, cno, degree from score;
需要用第一句話中的sname替換第二行的sno，下面使用多表查尋語句
select sname, cno, degree from student, score where student.sno=score.sno;
15、查尋所有學生的sno, cname和degree
select sno, cname, degree from course, score where course.cno=score.cno;
16、查詢所有學生的sname、cname、degree列（來自三張表）
select sname, cname, degree from student, course, score where student.sno=score.sno and course.cno=score.cno;
select sname, cname, degree, student.sno as stu_sno, course.cno from student, course, score where student.sno=score.sno and course.cno=score.cno;
因爲sno有歧義所以要加student.sno，可以用as去改名
17、查詢95031班學生每門課的平均分
select cno, avg(degree) from score where sno in (select sno from student where sclass='95031') group by cno;
18、查詢選修“3-105”課程的成績高於109號同學“3-105”成績的所有同學記錄
select * from score where cno='3-105' and degree>(select degree from score where sno='109' and cno='3-105');
19、查詢成績高於學號爲"109"、課程號爲"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');
20、查詢和學號108、101的同學童年出生的所有學生的sno、sname和sbirthday列
select sno,sname,sbirthday from student where year(sbirthday) in (select year(sbirthday) from student where sno in (108,101));
21、查詢“張旭”教師任課的學生成績
select degree from score where cno=(select cno from course where tno=(select tno from teacher where tname='張旭'));
22、查詢選修某課程的同學多於5人的教師姓名
select tname from teacher where tno = (select tno from course where cno=(select cno from score group by cno having count(*) > 5));
23、查詢95033和95031班全體學生記錄
select * from student where sclass in ('95033', '95031');
24、查詢85分以上成績的課程cno
select cno from score where degree>85;
25、查詢出“計算機系”教師所有課程的成績表
select * from score where cno in(select cno from course where tno in (select tno from teacher where depart='計算機系'));
26、查詢計算機系和電子工程系不同職稱的教師的tname和prof（職稱在別的部門沒有出現過）
union求並集
select * from teacher where depart='計算機系' and prof not in (select prof from teacher where depart='電子工程系')
union
select * from teacher where depart='電子工程系' and prof not in (select prof from teacher where depart='計算機系');
27、查詢選修編號爲3-105，且至少高於選修編號爲3-245的同學的信息並按照degree降序排列
（至少表示大於其中任意一個，用any）
select * from score where cno = '3-105' and degree > any(select degree from score where cno = '3-245') order by degree desc;
28、查詢選修編號爲3-105，且成績高於選修編號爲3-245的同學的信息
（且表示大於所有選項，用all）
select * from score where cno = '3-105' and degree > all(select degree from score where cno = '3-245’);
29、查詢所有教師和同學的name、sex和birthday(別名as，默認會寫第一組的名字所以只要改第一組的名字就ok)
select sname as name, ssex as sex, sbirthday as birthdy from student
union
select tname,tsex,tbirthday from teacher;
30、查詢所有女教師和女同學的name、sex和birthday
select sname as name, ssex as sex, sbirthday as birthday from student where ssex = '女'
union
select tname, tsex, tbirthday from teacher where tsex = '女';
31、查詢成績比該課程平均成績低的同學的成績表
select cno, avg(degree) from score group by cno;//查詢一類課程的平均分
select * from score a where degree < (select avg(degree) from score b where a.cno = b.cno);
32、查詢所有任課教師的tname和depart(任課說明在課程表中有課程)
select tname, depart from teacher where tno in (select tno from course);
33、查詢至少有兩名男生的班號(加條件分組篩選)
select sclass from student where ssex = '男' group by sclass having count(*)>1;
34、查詢student表中不姓王的同學記錄
select * from student where sname not like '王%';
35、查詢student表中每個學生的姓名和年齡
年齡=當前年份-出生年份
select sname, year(now())-year(sbirthday) from student;
36、查詢student表中最大最小sbirthday日期值
select sbirthday from student order by sbirthday;
select max(sbirthday) as '最大',min(sbirthday) as '最小' from student;
37、以班號和年齡從大到小排序查詢student表中的全部記錄
select * from student order by sclass desc, year(now)-year(sbirthday) desc;
select * from student order by sclass desc, sbirthday;
38、查詢男教師及其所教的課程
select cname from course where tno in (select tno from teacher where tsex='男');
39、查詢最高分同學的sno、cno和degree列
select * from score where degree = (select max(degree) from score);
40、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');
41、查詢和李軍同性別並且同班的同學的sname
select sname from student where ssex = (select ssex from student where sname = '李軍') and sclass = (select sclass from student where sname = '李軍');
42、查詢所有選修計算機導論課程的男同學的成績表
select * from score where sno in (select sno from student where ssex = '男') and cno = (select cno from course where cname = '計算機導論');
43、假設使用如下命令建立了一個grade表：
create table grade(
low int(3),
upp int(3),
grade 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(50,59,'E');
查詢所有同學的sno、cno和grade列
select sno,cno,grade from score,grade where degree between low and upp;