diff --git "a/38 \351\273\204\346\255\243\347\204\225/20230301 \347\254\254\344\272\224\346\254\241\344\275\234\344\270\232\345\217\212\347\254\224\350\256\260.md" "b/38 \351\273\204\346\255\243\347\204\225/20230301 \347\254\254\344\272\224\346\254\241\344\275\234\344\270\232\345\217\212\347\254\224\350\256\260.md"
new file mode 100644
index 0000000000000000000000000000000000000000..c095144e9f65b578e4fd8f20e8bd3fb432458871
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+++ "b/38 \351\273\204\346\255\243\347\204\225/20230301 \347\254\254\344\272\224\346\254\241\344\275\234\344\270\232\345\217\212\347\254\224\350\256\260.md"
@@ -0,0 +1,220 @@
+## 分组函数
+
+所有函数都带括号
+
+avg：平均值
+
+max：最大
+
+min：最小
+
+count：统计
+
+sum：求和
+
+select 函数（字段名）from 表名；
+
+select 函数（函数（字段名））from 表名
+
+## 联表查询
+
+两个或多个表一起查询
+
+条件：两个表必须有关联
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+分组要求，group by分组字段
+
+having 在统计中在次筛选
+
+拼接字符串
+
+例如：concat（x，y，z）
+
+concat_ws（"连接符",x,y）
+
+自连接：一张表当两张表用，都要写别名，为了区分
+
+笛卡尔积:无关联条件每一个都会匹配一遍会相乘
+
+## 作业
+
+```mysql
+create database school charset utf8;
+use school;
+-- 创建学生表结构
+DROP TABLE student;
+create table student(
+sno varchar(20) primary key,
+sname varchar(20) not null,
+ssex varchar(20) not null,
+sbirthday datetime,
+class varchar(20)
+);
+-- 添加学生数据
+insert into student values(108,'曾华','男','1977-9-1',95033);
+insert into student values(105,'匡明','男','1975-10-2',95031);
+insert into student values(107,'王丽','男','1976-1-23',95033);
+insert into student values(101,'李军','男','1976-2-20',95033);
+insert into student values(109,'王芳','男','1975-2-10',95031);
+insert into student values(103,'陆君','男','1974-6-3',95031);
+select * from student;
+-- 创建课程表结构
+show TABLES
+drop table course;
+create table course(
+cno varchar(20),
+cname varchar(20) not null,
+tno varchar(20) not null,
+primary KEY (cno,tno)
+ );
+alter table course add foreign key (tno) references teacher(tno);
+-- 添加课程数据
+insert into course values('3-105','计算机导论','825');
+insert into course values('3-245','操作系统','804');
+insert into course values('6-166','数字电路','856');
+insert into course values('9-888','高等数学','831');
+ select * from course;
+-- 创建成绩表结构
+DROP TABLE score;
+create table score(
+sno varchar(20) not null,
+cno varchar(20) not null,
+degree decimal(4,1),
+PRIMARY KEY(sno,cno),
+FOREIGN KEY (sno) REFERENCES student(sno),
+FOREIGN KEY (cno) REFERENCES course(cno)
+);
+-- 添加成绩
+insert into score values(103,'3-245',86);
+insert into score values(105,'3-245',75);
+insert into score values(109,'3-245',68);
+insert into score values(103,'3-105',92);
+insert into score values(105,'3-105',88);
+insert into score values(109,'3-105',76);
+insert into score values(101,'3-105',64);
+insert into score values(107,'3-105',91);
+insert into score values(108,'3-105',78);
+insert into score values(101,'6-166',85);
+insert into score values(107,'6-166',79);
+insert into score values(108,'6-166',81);
+select * from score;
+-- 创建老师表结构
+DROP TABLE teacher
+create table teacher(
+tno VARCHAR(20)PRIMARY KEY,
+tname varchar(20) not null,
+tsex varchar(20) not null,
+tbirthday datetime,
+prof varchar(20),
+depart varchar(20)
+);
+SELECT * FROM teacher;
+DESC teacher;
+show TABLES;
+-- 添加教师数据
+insert into teacher values (804,'李诚','男','1958-12-2','副教授','计算机系');
+insert into teacher values (856,'张旭','男','1969-3-12','讲师','电子工程系');
+insert into teacher values (825,'王萍','女','1972-5-5','助教','计算机系');
+insert into teacher values (831,'刘冰','女','1977-8-14','助教','电子工程系');
+
+-- 题目
+-- 1.查询所有学生,都学了那些课程,要显示学生信息和课程信息
+ select
+ stu.*,c.*
+ from
+ student stu
+ left join score s on stu.sno = s.sno
+ left join course c on s.cno = c.cno;
+-- 2.查询没有学生的教师所有信息
+ select
+ t.*
+ from
+ teacher t
+ left join course c on c.tno = t.tno
+ left join score s on s.cno=c.cno
+ where sno is null;
+-- 3.查询score表中得最高分的学生学号和课程号
+select max(degree),sno,cno from score;
+select sno,cno,degree from score where degree = ( select MAX( degree ) from score );
+-- 4.查询所有学生的sname cno degree列
+select sname,cno,degree from student,score;
+-- 5.查询所有学生的sno cname degree列
+select sno,cname,degree from course,score;
+-- 6.查询所有学生的sname cname degree列
+select sname,cname,degree from course,score,student;
+-- 7.查询 95033 班学生得平均分
+select AVG(degree) from student,score where Class=95033;
+-- 8.查询选修 3-105 课程得成绩高于 109 号同学成绩的所有同学的记录
+select a.* from score a inner join score b on a.cno=b.cno where a.cno='3-105' and b.sno=109 and a.degree > b.degree order by a.sno;
+-- 9.查询score中选学多门课程得同学中 分数非最高分成绩的记录
+select MAX(degree) from score;
+select sno,cno,degree from score where degree != (select MAX(degree) from score);
+-- 10.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 cno='3-105' and degree>(select degree from score where cno='3-105' and sno='109');
+-- 11.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');
+-- 12.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';
+-- 13.查询选修某课程的同学人数多于5人的教师姓名。
+select tname from course co,teacher te where co.tno=te.tno and cno=(select cno from score group by cno having count(*)>5);
+-- 14.查询出“计算机系“教师所教课程的成绩表。
+select sc.* from course co, score sc where co.cno = sc.cno and co.tno in(select tno from teacher where depart='计算机系');
+-- 15.查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
+select tname ,prof from teacher where depart='计算机系'
+union
+select tname ,prof from teacher where depart='电子工程系';
+-- 16.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 cno,sno,degree from score where cno='3-105' and degree>all(select degree from score where cno='3-245') order by degree desc;
+-- 17.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 * from score where cno='3-105' and degree>all(select degree from score where cno='3-245');
+-- 18.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 a.degree<(select avg(degree) from score b where a.cno=b.cno);
+-- 19.查询所有任课教师的Tname和Depart.
+select tname,depart from teacher;
+-- 20.查询所有未讲课的教师的Tname和Depart.
+select te.tname,te.depart from teacher te left join course co on te.tno = co.tno left join score sc on co.cno = sc.cno where sc.sno is null ;
+-- 21.查询“男”教师及其所上的课程。
+select * from teacher te,course co where te.tno=co.tno and tsex='男';
+-- 22.查询最高分同学的Sno、Cno和Degree列。
+select sno,cno,degree from score where cno in(select cno from score group by cno) and degree in (select max(degree) from score group by cno);
+-- 23.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');
+-- 24.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');
+-- 25.查询所有选修“计算机导论”课程的“男”同学的成绩表。
+select * from student st , score sc ,course co where st.sno=sc.sno and co.cno=sc.cno and st.ssex='男' and co.cname='计算机导论';
+
+```
+
diff --git "a/38 \351\273\204\346\255\243\347\204\225/20230306 \347\254\254\345\205\255\346\254\241\344\275\234\344\270\232\345\217\212\347\254\224\350\256\260.md" "b/38 \351\273\204\346\255\243\347\204\225/20230306 \347\254\254\345\205\255\346\254\241\344\275\234\344\270\232\345\217\212\347\254\224\350\256\260.md"
new file mode 100644
index 0000000000000000000000000000000000000000..d072296584405da2ba4dfd8cd921cf72ccaaa076
--- /dev/null
+++ "b/38 \351\273\204\346\255\243\347\204\225/20230306 \347\254\254\345\205\255\346\254\241\344\275\234\344\270\232\345\217\212\347\254\224\350\256\260.md"
@@ -0,0 +1,134 @@
+## 子查询
+
+嵌套在其他sql语句中的select语句
+
+子查询的结果
+
+可能作为外层查询的条件，数据源及要查的结果
+
+形式一：
+
+放在select后，单列单值
+
+形式二:
+
+放在where/having后 单列单值、单列多值
+
+形式三：
+
+放在from后面 多列多值
+
+select （形式一）from （形式三） where （形式二）
+
+## 作业
+
+```mysql
+drop database zcx;
+create database zcx charset utf8;
+use zuoye;
+SHOW TABLES;
+-- 学生信息表
+create table stuinfo(
+stuNo varchar(10) primary key,
+stuName varchar(10) not null,
+stuSex enum('男','女'),
+stuAge int,
+stuAddress varchar(20),
+stuSeat int
+);
+DROP TABLE stuinfo;
+insert into stuinfo values('s2501','张秋利','男',20,'美国硅谷',1);
+insert into stuinfo values('s2502','李斯文','女',18,'湖北武汉',2);
+insert into stuinfo values('s2503','马文才','男',18,'湖南长沙',3);
+insert into stuinfo values('s2504','欧阳俊雄','女',21,'湖北武汉',4);
+insert into stuinfo values('s2505','梅超风','男',20,'湖北武汉',5);
+insert into stuinfo values('s2506','陈旋风','男',19,'美国硅谷',6);
+select * from stuinfo;
+desc stuinfo;
+-- 成绩表
+create table stuExam(
+examNo int not null primary key,
+stuNo varchar(10) not null,
+writterExam int,
+labExam int
+);
+insert into stuExam values(1,'s2501',50,70);
+insert into stuExam values(2,'s2502',60,65);
+insert into stuExam values(3,'s2503',86,70);
+insert into stuExam values(4,'s2504',40,80);
+insert into stuExam values(5,'s2505',70,85);
+insert into stuExam values(6,'s2506',85,90);
+select * from stuExam;
+desc stuExam;
+-- 成绩表
+drop table stuMarks;
+create table stuMarks(
+examNo int not null primary key,
+stuID varchar(10) not null,
+score int
+);
+insert into stuMarks values(1,'s2501',88);
+insert into stuMarks values(2,'s2501',92);
+insert into stuMarks values(3,'s2501',53);
+insert into stuMarks values(4,'s2502',60);
+insert into stuMarks values(5,'s2502',99);
+insert into stuMarks values(6,'s2503',82);
+select * from stuMarks;
+desc stuMarks;
+-- 在如图的数据表上完成以下题目
+-- 1.查询出年龄比班上平均年龄大的学生的信息
+select avg(stuAge) from stuinfo;
+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
+ stui.stuNo,
+ stui.stuName,
+ stui.stuSex,
+ max( score )
+FROM
+ stuMarks stum
+ RIGHT JOIN stuinfo stui ON stum.stuID = stui.stuNo
+GROUP BY
+ stuID;
+-- 3.查询出每个学生的学号，姓名，性别和考试平均分（stuExam）
+ select *,avg(writterExam + labExam) from stuExam GROUP BY stuNo;
+
+SELECT stui.stuNo, stui.stuName, stui.stuSex,( writterExam + labExam )/ 2
+FROM
+ stuExam stue
+ RIGHT JOIN stuinfo stui ON stue.stuNo = stui.stuNo
+GROUP BY
+ stui.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 stuage FROM stuinfo WHERE stusex = '男';
+SELECT * FROM stuinfo WHERE stusex = '女'and stuage>ALL(SELECT 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 * FROM stumarks;
+ SELECT * FROM stuinfo LEFT JOIN stumarks ON stuinfo.stuno = stumarks.stuid
+ WHERE 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 DISTINCT * from stuMarks stum right join stuinfo stui on stum.stuID=stui.stuNo where stum.score is not null ;
+-- 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 * from stuMarks stum right join stuinfo stui on stum.stuID=stui.stuNo where stum.score is null;
+-- 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 * from stuMarks stum right join stuinfo stui on stum.stuID=stui.stuNo where stum.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 stumarks;
+SELECT AVG(score),stuinfo.* FROM stumarks RIGHT JOIN stuinfo ON stumarks.stuid = stuinfo.stuno GROUP BY examno,stuinfo.stuno 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 max(score) from stumarks;
+select score from stumarks where stuid='s2501';
+select * from stuinfo left join stumarks on stuno = stuid where score>all(select score from stumarks where 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 score FROM stumarks WHERE stuid = 's2501';
+SELECT * FROM stumarks WHERE score > ANY(SELECT score FROM stumarks WHERE stuid = 's2501')
+-- 13.查询班上比所有男生年龄都要大的女生的信息
+ select max(stuage) from stuinfo where stusex='男';
+ select * from stuinfo where stusex = '女' and 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 stuage FROM stuinfo WHERE stusex = '男';
+ SELECT * FROM stuinfo WHERE stusex = '女' AND stuage>any(SELECT stuage FROM stuinfo WHERE stusex = '男');
+```
+