diff --git "a/25 \346\234\261\346\203\240\345\277\240/20230302 mysql\350\201\224\350\241\250.md" "b/25 \346\234\261\346\203\240\345\277\240/20230302 mysql\350\201\224\350\241\250.md"
new file mode 100644
index 0000000000000000000000000000000000000000..48698116376d5337cb89f4d01e3d22af47b56160
--- /dev/null
+++ "b/25 \346\234\261\346\203\240\345\277\240/20230302 mysql\350\201\224\350\241\250.md"	
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+````mysql
+-- 1.	设有一数据库，包括四个表：学生表（Student）、课程表（Course）、成绩表（Score）以及教师信息表（Teacher）。四个表的结构分别如表1-1的表（一）~表（四）所示，数据如表1-2的表（一）~表（四）所示。用SQL语句创建四个表并完成相关题目。
+-- 2.	数据库的表结构
+create database class3 charset utf8;
+use class3;
+
+create table Student(
+Sno varchar(20) not null primary key comment '学号(主码)',
+Sname varchar(20) not null comment '学号姓名',
+Ssex varchar(20) not null comment '学生性别',
+Sbirthday datetime null comment '学生出生年月',
+Class varchar(20) null comment '学生所在班级'
+);
+
+create table Course(
+Cno varchar(20) not null primary key comment '课程号(主码)',
+Cname varchar(20) not null comment '课程名称',
+Tno varchar(20) not null comment '教工编号(外码)',
+foreign key (Tno) references Teacher(Tno)
+);
+
+create table Score(
+Sno varchar(20) not null comment '学号(外码)',
+Cno varchar(20) not null comment '课程号(外码)',
+Degree Decimal(4,1) null comment '成绩',
+primary key (Sno,Cno),
+foreign key (Sno) references Student(Sno),
+foreign key (Cno) references Course(Cno)
+);
+
+create table Teacher(
+Tno varchar(20) not null primary key comment '教工编号(主码)',
+Tname varchar(20) not null comment '教工姓名',
+Tsex varchar(20) not null comment '教工性别',
+Tbirthday datetime null comment '教工出生日期',
+Prof varchar(20) null comment '职称',
+Depeat varchar(20) not null comment '教工所在部门'
+);
+-- 3.	数据库中的数据:
+-- 1,查询所有学生，都学了哪些课程，要显示学生信息和课程信息
+
+select *from Student stu,Course c,Score s where c.Cno = s.Cno and stu.Sno = s.Sno;
+
+select *from Score s
+inner join Course c  on c.Cno = s.Cno
+inner join  Student stu on stu.Sno = s.Sno;
+
+-- 2，查询没有学生的教师的所有信息
+
+select *from Teacher t,Score s, Course c where t.Tno=c.Tno and c.Cno= s.Cno;
+
+select *from Course c left join Teacher t on t.Tno=c.Tno
+left join Score s on  c.Cno= s.Cno where Sno is null;
+
+insert into Student values
+('108','曾华','男','1977-9-1','95033'),
+('105','匡明','男','1975-10-2','95031'),
+('107','王丽','女','1976-1-23','95033'),         
+('101','李军','男','1976-2-20','95033'), 
+('109','王芳','女','1975-2-10','95031'),
+('103','陆军','男','1974-6-3','95031');
+
+insert into Course values
+('3-105','计算机导论','825'),
+('3-245','操作系统','804'),
+('6-166','数字电路','856'),
+('9-888','高等数学','831');
+
+insert into Score values
+('103','3-245','86'),
+('105','3-245','75'),
+('109','3-245','68'),
+('103','3-105','92'),
+('105','3-105','88'),
+('109','3-105','76'),
+('101','3-105','64'),
+('107','3-105','91'),
+('108','3-105','78'),
+('101','6-166','85'),
+('107','6-166','79'),
+('108','6-166','81');
+
+insert into Teacher values
+('804','李诚','男','1958-12-2','副教授','计算机系'),
+('856','张旭','男','1969-3-12','讲师','电子工程系'),
+('825','王萍','女','1972-5-5','助教','计算机系'),
+('831','刘冰','女','1977-8-14','助教','电子工程系')
+-- 4.	查询
+-- 1查询Score表中的最高分的学生学号和课程号。
+select MAX(Degree) `Sno`, `Cno` from score;
+-- 2　查询所有学生的Sname、Cno和Degree列。
+select Sname 姓名,Cno,Degree  from student, score;
+-- 3　查询所有学生的Sno、Cname和Degree列。
+select Sno,Cname,Degree  from course,score;
+-- 4查询所有学生的Sname、Cname和Degree列。
+select Sname 姓名,Cname,Degree  from course,score,student;
+-- 5　查询“95033”班学生的平均分。
+select AVG(Degree) from student,score WHERE Class=95033;
+-- 6　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。
+SELECT * from score where cno='3-105' and degree>76;
+-- 7　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。
+(select max(degree) from score);
+select Degree from score where Degree != (select max(degree) from score)group by Degree;
+-- 8　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 student s,score se where s.Sno=se.Sno and Degree>  (select Degree from score where sno='109' and cno='3-105');
+-- 9　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 year(Sbirthday) from student where sno='108';
+select sno ,Sname,Sbirthday from student where year(Sbirthday)=(select year(Sbirthday) from student where sno='108');
+-- 10　查询“张旭“教师任课的学生成绩。
+select * from teacher where Tname='张旭';
+select Degree from teacher t ,course c ,score s where t.Tno=c.Tno and c.Cno=s.cno and t.Tname='张旭';
+-- 11　查询选修某课程的同学人数多于5人的教师姓名。
+select s.Cno from teacher t ,course c ,score s where t.Tno=c.Tno and c.Cno=s.cno group by c.Cno having count(s.Cno)>5;
+-- 12　查询出“计算机系“教师所教课程的成绩表。
+select tname ,prof from teacher where Depart='计算机系'
+union
+select tname ,prof from teacher where Depart='电子工程系';
+-- 13　查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
+select Degree from score where Cno='3-245';
+select * from score where Cno='3-105' and Degree >= all (select Degree from score where Cno='3-245') order by Degree desc ;
+-- 14　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。
+select * from score where Cno='3-105' and Degree > all (select Degree from score where Cno='3-245');
+-- 16　查询成绩比该课程平均成绩低的同学的成绩表。
+select avg(Degree) from score;
+select Degree from score where Degree< (select avg(Degree) from score);
+
+-- 17　查询所有任课教师的Tname和Depart.
+select Tname,Depart from teacher;
+-- 18　查询所有未讲课的教师的Tname和Depart.
+select Tname,Depart from teacher left join Course C on Teacher.Tno = C.Tno left join score s on C.Cno = s.Cno where Sno is null ;
+
+-- 19　查询“男”教师及其所上的课程。
+select t.*,c.Cname from teacher t ,course c where t.tno= c.Tno and t.Tsex='男';
+-- 20　查询最高分同学的Sno、Cno和Degree列。
+select * from score where Degree=(select max(Degree) from score);
+-- 21　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');
+-- 22　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');
+
+-- 23　查询所有选修“计算机导论”课程的“男”同学的成绩表
+select Ssex,Cname,Degree from student s,course c,score se where s.Sno=se.Sno and se.Cno=c.Cno and Cname='计算机导论' and Ssex='男';
+```
+````
+
+
+
diff --git "a/25 \346\234\261\346\203\240\345\277\240/20230307 \345\255\220\346\237\245\350\257\242.md" "b/25 \346\234\261\346\203\240\345\277\240/20230307 \345\255\220\346\237\245\350\257\242.md"
new file mode 100644
index 0000000000000000000000000000000000000000..f20b9dc16c712919838c8c2e0a4c087960cd0051
--- /dev/null
+++ "b/25 \346\234\261\346\203\240\345\277\240/20230307 \345\255\220\346\237\245\350\257\242.md"	
@@ -0,0 +1,84 @@
+```mysql
+CREATE DATABASE TEXT charset utf8;
+use text;
+CREATE table stuinfo(
+stuNo VARCHAR(10) primary key,
+stuName VARCHAR(10),
+stuSex  VARCHAR(10),
+stuAge VARCHAR(10),
+stuAddress VARCHAR(20),
+stuSeat INT
+);
+CREATE table stuExam(
+examNo int primary key auto_increment,
+stuNo VARCHAR(10),
+writtenExam int,
+labExam INT
+);
+CREATE table stuMarks(
+examNo int primary key auto_increment,
+stuID VARCHAR(10),
+score INT
+);
+alter table stuExam add foreign key (stuNO) references stuinfo(stuNO);
+alter table stuMarks add foreign key (examNo) references stuExam(examNo);
+
+
+INSERT into stuinfo VALUES
+('s2501','张秋利','男',20,'美国硅谷',1),
+('s2502','李斯文','女',18,'湖北武汉',2),
+('s2503','马文才','男',18,'湖南长沙',3),
+('s2504','欧阳俊雄','女',21,'湖北武汉',4),
+('s2505','梅超风','男',20,'湖北武汉',5),
+('s2506','陈旋风','男',19,'美国硅谷',6);
+
+INSERT INTO stuExam VALUES
+(1,'s2501',50,70),
+(2,'s2502',60,65),
+(3,'s2503',86,70),
+(4,'s2504',40,80),
+(5,'s2505',70,85),
+(6,'s2506',85,90);
+
+INSERT into stuMarks VALUES
+(1,'s2501',88),
+(2,'s2501',92),
+(3,'s2501',53),
+(4,'s2502',60),
+(5,'s2502',99),
+(6,'s2503',82);
+
+
+# 1.查询出年龄比班上平均年龄大的学生的信息
+select * from stuinfo where stuAge>(select avg(stuAge) from stuinfo);
+# 2.查询出每个学生的学号，姓名，性别和选修课程的最高分（stuMarks）
+select stuNo,stuName,stuSex,max(score) from stuinfo a left join stumarks b on a.stuNo=b.stuID group by stuNo;
+# 3.查询出每个学生的学号，姓名，性别和考试平均分（stuExam）
+select a.stuNo,a.stuName,a.stuSex,(b.writtenExam+b.labExam)/2 平均分 from stuinfo a left join stuexam b on a.stuNo=b.stuNo;
+# 4.查询性别是男并且年龄大于等于20的学生的信息(用两种方法实现：普通查询和子查询)
+select * from stuinfo where stuSex='男' and stuAge>=20;
+# 5.查询出年龄比所有男生年龄都大的女生的信息
+select * from stuinfo where stuAge>(select max(stuAge) from stuinfo where stuSex='男');
+# 6.查询出所有选修课程都及格的学生的信息   （stuMarks）
+SELECT a.* FROM stuinfo a LEFT JOIN stumarks b on a.stuNo=b.stuID GROUP BY stuID HAVING  min(score)>=60;
+# 7.查询出参加考试的学生的信息（用表连接，in二种方法做）（stuMarks）
+SELECT * FROM stuinfo a RIGHT JOIN stumarks b on a.stuNO=b.stuID GROUP BY stuID;
+SELECT * FROM stuinfo WHERE stuNo in (SELECT stuID FROM stumarks GROUP BY stuID);
+# 8.查询出没有参加考试的学生的信息（用表连接，in二种方法做）（stuMarks）
+SELECT a.* FROM stuinfo a LEFT JOIN stumarks b on a.stuNO=b.stuID WHERE score is null;
+select * from stuinfo where stuNo not in(select stuID from stumarks group by stuID);
+# 9.将有一门成绩成绩大于90分的学生的基本信息查询出来（stuMarks）
+SELECT a.* FROM stuinfo a LEFT JOIN stumarks b on a.stuNO=b.stuID GROUP BY stuID HAVING max(score)>90;
+# 10.查询出平均成绩在80分以上的学生的基本信息（stuMarks）
+SELECT * FROM stuinfo a LEFT JOIN stumarks b on a.stuNO=b.stuID GROUP BY stuID HAVING avg(score)>80;
+# 11.查询出某同学所有考试成绩比“张秋利”同学所有分数都高的学生基本信息（stuMarks）	
+SELECT * FROM stuinfo a LEFT JOIN stumarks b on a.stuNo=b.stuID WHERE score>(SELECT max(score)FROM stumarks WHERE stuID='s2501') AND stuID!='s2501';
+# 12.查询出某同学所有考试成绩只需要比“张秋利”同学某个分数高的学生基本信息（stuMarks）
+SELECT * FROM stuinfo a LEFT JOIN stumarks b on a.stuNo=b.stuID WHERE score>(SELECT min(score)FROM stumarks WHERE stuID='s2501') AND stuID!='s2501' GROUP BY stuID;
+# 13.查询班上比所有男生年龄都要大的女生的信息
+select * from stuinfo where stuAge>(select max(stuAge) from stuinfo where stuSex='男');
+# 14.查询出只是比某个男生年龄大的女生的信息
+select * from stuinfo where stuSex='女' and stuAge>(select min(stuAge) from stuinfo where stuSex='男');
+
+```
+