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+```mysql
+# 笔记
+
+子查询放在where,having后面
+单列单值直接用>,<,=等运算符
+单列多值用in,not in或搭配any使用
+子查询3种用法：select 子查询1 from 子查询2 where 子查询3
+
+
+create database student charset utf8;
+use student;
+CREATE TABLE stuinfo (
+ stuNO VARCHAR(20) PRIMARY KEY,
+ stuName VARCHAR(20),
+ stuSex enum('男','女'),
+ stuAge INT,
+ stuAddress VARCHAR(20),
+ stuSeat INT
+);
+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',22,'湖南长沙',3),('s2504','欧阳俊熊','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);
+UPDATE stuinfo set stuage = (18) WHERE stuNo = 's2503';
+CREATE TABLE stuExam(
+	examNo INT,
+	stuNo VARCHAR(20),
+	writtenExam INT,
+	labExam INT,
+	PRIMARY KEY(examNO,stuNo),
+	FOREIGN KEY (stuNo) REFERENCES stuinfo(stuNo)
+);
+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);
+CREATE TABLE stuMarks(
+	examNo INT PRIMARY KEY,
+	stuID VARCHAR(20),
+	score int,
+	FOREIGN KEY (examNo) REFERENCES stuExam(examNo)
+);
+ALTER TABLE stumarks ADD FOREIGN KEY (stuid) REFERENCES stuinfo(stuno);
+INSERT INTO stumarks VALUES(1,'s2501',88),(2,'s2501',92),(3,'s2501',53),(4,'s2502',60),(5,'s2502',99),(6,'s2503',82);
+-- 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 stuage>=20 and stusex='男';
+SELECT * from (SELECT * from stuinfo where stuage>=20 and stusex='男') as acx;
+-- 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') and stusex='女';
+-- 
+
+-- 6.查询出所有选修课程都及格的学生的信息   （stuMarks）
+
+SELECT * from stumarks left join stuinfo on stumarks.stuid=stuinfo.stuno where stuid != any(select stuid from stumarks 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 stuinfo.* from stumarks left join stuinfo on stumarks.stuid=stuinfo.stuno GROUP BY stuno;
+
+SELECT * from stuinfo where stuno in (SELECT stuid from stumarks);
+-- 
+
+-- 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 stuinfo.* from stumarks right join stuinfo on stumarks.stuid=stuinfo.stuno where score is null GROUP BY stuno;
+
+SELECT * from stuinfo where stuno not in (SELECT stuid from stumarks);
+-- 
+
+-- 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 stuinfo.* from stumarks left join stuinfo on stumarks.stuid=stuinfo.stuno where stuid = any(select stuid from stumarks where score>90) GROUP BY stuid;
+-- 
+
+-- 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 where stuno in
+
+(SELECT stuid from stumarks WHERE 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 stuinfo.* from stuinfo inner join stumarks on stumarks.stuid=stuinfo.stuno where score>(
+
+select max(score) from stuinfo inner join stumarks on stumarks.stuid=stuinfo.stuno where stuname ='张秋利') GROUP BY stuname;
+-- 
+
+-- 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 stuinfo.* from stuinfo inner join stumarks on stumarks.stuid=stuinfo.stuno where score> any(
+
+select score from stuinfo inner join stumarks on stumarks.stuid=stuinfo.stuno where stuname ='张秋利') and stuname != '张秋利' GROUP BY stuname;
+-- 
+
+-- 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') and stusex='女';
+-- 
+
+-- 14.查询出只是比某个男生年龄大的女生的信息
+
+select * from stuinfo where stuage> any(SELECT stuage from stuinfo where stusex='男') and stusex='女';
+-- 
+```
+