From 061e37e390946e0bf321cccdec1b4e796aae4974 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2?= <11785154+yan-xuelian@user.noreply.gitee.com> Date: Wed, 1 Mar 2023 08:23:44 +0000 Subject: [PATCH 1/7] =?UTF-8?q?=E5=88=A0=E9=99=A4=E6=96=87=E4=BB=B6=2037?= =?UTF-8?q?=20=E9=97=AB=E9=9B=AA=E8=8E=B2/20230227=20=E5=85=B3=E8=81=94?= =?UTF-8?q?=E6=9F=A5=E8=AF=A2.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...63\350\201\224\346\237\245\350\257\242.md" | 203 ------------------ 1 file changed, 203 deletions(-) delete mode 100644 "37 \351\227\253\351\233\252\350\216\262/20230227 \345\205\263\350\201\224\346\237\245\350\257\242.md" diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230227 \345\205\263\350\201\224\346\237\245\350\257\242.md" "b/37 \351\227\253\351\233\252\350\216\262/20230227 \345\205\263\350\201\224\346\237\245\350\257\242.md" deleted file mode 100644 index 94a45bf..0000000 --- "a/37 \351\227\253\351\233\252\350\216\262/20230227 \345\205\263\350\201\224\346\237\245\350\257\242.md" +++ /dev/null @@ -1,203 +0,0 @@ -```sql -create database zuoye2 charset utf8; -use zuoye2; - -create table student( - sno varchar(20)primary key, - sname varchar(20)not null, - ssex varchar(20)not null, - sbirthday datetime, - class varchar(20) -); -``` - -```sql -create table course( - cno varchar(20)primary key, - cname varchar(20) not null, - tno varchar(20)not null, - foreign key (tno) references teacher(tno) -); -``` - -```sql -create table score( - sno varchar(20)not null, - cno varchar(20)not null, - degree decimal(4,1), - foreign key (sno) references student(sno), - foreign key (cno) references course(cno) -); -``` - -```sql -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)not null -); -``` - -```sql -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','女','1976-1-23','95033'); -insert into student values(101,'李军','男','1976-2-20','95033'); -insert into student values(109,'王芳','女','1975-2-10','95031'); -insert into student values(103,'陆君','男','1974-6-3','95031'); - -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'); - -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'); - -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'); -``` - -- - -```sql -- 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 student.sno,sname,ssex,sbirthday,class,cname -from student left join score on student.sno=score.sno -left join course on score.cno=course.cno; --- 2，查询没有学生的教师的所有信息\ -select tname from -teacher left join course on teacher.tno=course.tno -left join score on course.cno=score.cno -left join student on score.sno=student.sno -where min(lishi( -select count(score.cno),cname as rshu from -score right join course on score.cno=course.cno group by course.cno)); --- 不会做别抄 - -select * from teacher; -select * from score; - -select * from course; --- - --- 4.查询 --- ①　查询Score表中的最高分的学生学号和课程号。 -select sno,cno from score where degree=(select max(degree) from score); --- ②　查询所有学生的Sname、Cno和Degree列。 -select sname,score.cno,degree from student inner join score on student.sno=score.sno; --- ③　查询所有学生的Sno、Cname和Degree列。 -select score.sno,cname,degree from score inner join course on score.cno=course.cno; --- ④　查询所有学生的Sname、Cname和Degree列。 -select sname,cname,degree from student inner join score on student.sno=score.sno inner join course on score.cno=course.cno; --- ⑤　查询“95033”班学生的平均分。 -select avg(score.Degree) from score inner join student on student.Sno = score.Sno where student.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 student -inner join score on student.sno=score.sno -where score.cno='3-105' and degree > -(select degree from score where score.sno=109 and score.cno='3-105' ); --- 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(score.degree) from score where 1< (select count(sno) from score) -select count(sno) from score group by sno --- 不会做别抄 --- 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 score -where degree>( -select degree from score where score.sno=109 and score.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 sno,sname,sbirthday from -student where sbirthday=(select sbirthday from student where sno=108); --- 这个只有他自己生日一样下面是不输出他自己生日的代码 -select sno,sname,sbirthday from student -where sbirthday=(select sbirthday from student where sno=108) -and sno!=108; --- ⑩　查询“张旭“教师任课的学生成绩。 -select degree from score left join course -on score.cno=course.cno -left join teacher -on course.tno=teacher.tno -where score.cno=( -select course.cno from course left join teacher -on course.tno=teacher.tno -where 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 tname from teacher left join course -on teacher.tno=course.tno -left join score -on course.cno=score.cno -where (select count(score.cno) from score group by cno ) --- 不会做 --- ⑫　查询出“计算机系“教师所教课程的成绩表。 -select score.sno,score.cno,degree from score left join course -on score.cno=course.cno -left join teacher -on course.tno=teacher.tno -where depart='计算机系'; - --- 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 tname,prof from teacher where prof in (select distinct prof from teacher); --- 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 score.cno,score.sno,score.degree from -score inner join course -on score.cno = course.cno -and score.cno = '3-105' -and score.degree > ( -select max(degree) from score where score.cno='3-245') -order by score.degree desc; --- ⑮　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 score.cno,score.sno,score.degree from -score inner join course -on score.cno = course.cno -and score.cno = '3-105' -and score.degree > ( -select max(degree) from score where score.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 degree --- ⑰　查询所有任课教师的Tname和Depart. -select tname,depart from teacher --- 不会做 --- ⑱　查询所有未讲课的教师的Tname和Depart. -select tname,depart from teacher --- 不会做 --- ⑲　查询“男”教师及其所上的课程。 -select tname,cname from teacher left join course -on teacher.tno=course.tno -where tsex='男'; --- ⑳　查询最高分同学的Sno、Cno和Degree列。 -select sno,cno,degree 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 score.* from score left join course -on score.cno=course.cno -left join student -on score.sno=student.sno -where score.cno=(select course.cno from course where cname='计算机导论') - -and ssex='男'; --- -``` - -- Gitee From 0fcc47fc3df0dbc213ed4d74a1f5a4bf64c86b80 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84=E4=BD=9C=E4=B8=9A?= <1653483984@qq.com> Date: Tue, 7 Mar 2023 23:37:05 +0800 Subject: [PATCH 2/7] =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84?= =?UTF-8?q?=E4=BD=9C=E4=B8=9A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...6 \345\255\220\346\237\245\350\257\242.md" | 163 ++++++++++++++++++ 1 file changed, 163 insertions(+) create mode 100644 "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" new file mode 100644 index 0000000..3a31ead --- /dev/null +++ "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" @@ -0,0 +1,163 @@ +# 1.笔记 + +### 什么子查询 + +-- 嵌套在其它SQL语句中的select语句 +-- 子查询通常在外层语句之前优先执行，所以要用（）包括起来 +-- 子查询的结果，一般作为外层语句的条件，数据源等 + +select ① from ③ where ②; + +### 形式一,select后面嵌套子查询 + +where 后面不支持聚合函数和别名，having支持聚合也支持别名 + +### 形式二，在where/having 后面做条件 + +当子查询放在where 、 having 后面当条件用是，有几种情况 + ① 单列单个值，可以直接用>,<,<=...!=，这些比较运算符 + ② 单列多个值，要用in,not in 这种集合的比较 + ③ 单列多个值，可以用>,<,<=...!=，比较运算符，搭配any,all 这些关键字，一起使用 + +### 形式三，在from后面,形成一个临时表，必须加一个别名 + +子查询的结果： +单列单个值：可以放在select 后，也可以放where/having之后 +单列多个值：where后，或having后 ，不用直接用<,=,>= 这种单纯的比较运算符。但可以用搭配any(任意一个),all(所有的)等关键字一起使用。还可以用in,not in这种表达式 + +多列时，只能当临时表来表用，放在from后面，而且必须，给他取个别名 + +# 2.作业 + +```mysql +create database yxll charset utf8; +use yxll; +create table stuinfo( +stuNO varchar(6) , +stuName varchar(6), +stuSex varchar(4), +stuAge varchar(4) , +stuAddress varchar(10), +stuSeat varchar(4) +); +desc stuinfo; +INSERT into stuinfo values('s2501','张秋利','男',20,'美国硅谷',1), + ('s2502','李斯才','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); + select *from stuinfo; + + +create table stuExam( +examNO varchar(3), +stuNO varchar(6), +writtenExam varchar(4), +labExam varchar(4) +); +desc stuExam; +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'); + +select *from stuExam ; + +create table stuMarks( +examNO varchar(3), +stuID varchar(6), +score varchar(4) +); +desc stuMarks; +INSERT into stuMarks values('1','s2501','88'), + ('2','s2502','92'), + ('3','s2503','53'), + ('4','s2504','60'), + ('5','s2505','99'), + ('6','s2506','82'); + + +select *from 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 * 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 max(score) from stuMarks; + SELECT stuinfo.stuNO, stuName, stuSex, (SELECT max(score) from stuMarks ) from stuinfo left join stuMarks on stuinfo.stuNO=stuMarks.stuID ; + + +-- 3.查询出每个学生的学号，姓名，性别和考试平均分（stuExam） +SELECT (labExam+writtenExam)/2 from stuExam ; +SELECT stuinfo.stuNO, stuName, stuSex,(SELECT (labExam+writtenExam)/2 ) from stuinfo left join stuExam on stuinfo.stuNO=stuExam.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; +select * from (select * from stuinfo where stuage>=20) a where stusex='男'; + +-- 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 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 stuinfo left join stuMarks on stuinfo.stuNO=stuMarks.stuID where score>=60; +-- + +select * from stuinfo a INNER JOIN stumarks b on a.stuNo = b.stuID where a.stuNo != (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 * FROM stuinfo a inner join stumarks b on a.stuNo = b.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 * FROM stuinfo a inner join stumarks b on a.stuNo = b.stuID where 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 stuinfo inner join stuMarks on stuinfo.stuNO=stuMarks.stuID where stuMarks.score>90; +-- + +-- 10.查询出平均成绩在80分以上的学生的基本信息（stuExam） + +SELECT * from stuexam where stuexam.score >((labExam+writtenExam)/2 ); +-- + +select * from stuinfo where stuno = (select stuno from stuexam where (writtenExam+labExam)/2>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 stuExam b on a.stuNo = b.stuNo where writtenExam>(select writtenExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')) AND labExam>(select labExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')); + +-- 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 stuExam b on a.stuNo = b.stuNo where writtenExam>(select writtenExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')) OR labExam>(select labExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')); + +-- 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 stuSex='女'and stuage>all(SELECT 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>any(SELECT stuage from stuinfo where stuSex='男'); + + +``` + -- Gitee From 02d1c1a45692869d85ca0f439ab85739dc696de0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2?= <1653483984@qq.com> Date: Tue, 7 Mar 2023 23:47:54 +0800 Subject: [PATCH 3/7] =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84?= =?UTF-8?q?=E4=BD=9C=E4=B8=9A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...46\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" | 0 1 file changed, 0 insertions(+), 0 deletions(-) rename "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" => "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" (100%) diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" similarity index 100% rename from "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" rename to "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" -- Gitee From acca35a5be6683f45eb7a7e18265e1d2735f222d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2?= <1653483984@qq.com> Date: Tue, 7 Mar 2023 23:56:00 +0800 Subject: [PATCH 4/7] =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84?= =?UTF-8?q?=E4=BD=9C=E4=B8=9A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...47\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" | 0 1 file changed, 0 insertions(+), 0 deletions(-) rename "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" => "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" (100%) diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" similarity index 100% rename from "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\345\222\214\344\275\234\344\270\232.md" rename to "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" -- Gitee From aae59c8a8a1f0dac5273fcd23a4b886d16ce745b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2?= <1653483984@qq.com> Date: Wed, 8 Mar 2023 00:07:39 +0800 Subject: [PATCH 5/7] =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84?= =?UTF-8?q?=E4=BD=9C=E4=B8=9A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...37\245\350\257\242\344\270\216\344\275\234\344\270\232.md" | 4 ++++ 1 file changed, 4 insertions(+) rename "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" => "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" (99%) diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" similarity index 99% rename from "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" rename to "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" index 3a31ead..dbbeaa5 100644 --- "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\347\232\204\347\254\224\350\256\260\345\222\214\344\275\234\344\270\232.md" +++ "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" @@ -19,6 +19,10 @@ where 后面不支持聚合函数和别名，having支持聚合也支持别名 ② 单列多个值，要用in,not in 这种集合的比较 ③ 单列多个值，可以用>,<,<=...!=，比较运算符，搭配any,all 这些关键字，一起使用 + + + + ### 形式三，在from后面,形成一个临时表，必须加一个别名 子查询的结果： -- Gitee From 56f02a11a7a194ebdabe461376424eb9440becf2 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2?= <1653483984@qq.com> Date: Wed, 8 Mar 2023 00:19:46 +0800 Subject: [PATCH 6/7] =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84?= =?UTF-8?q?=E4=BD=9C=E4=B8=9A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../20230306 \345\255\220\346\237\245\350\257\242.md" | 0 1 file changed, 0 insertions(+), 0 deletions(-) rename "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" => "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" (100%) diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" similarity index 100% rename from "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242\344\270\216\344\275\234\344\270\232.md" rename to "37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" -- Gitee From 79460984f765fbeccd0d9907ac293a5ccdf922ef Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2?= <1653483984@qq.com> Date: Wed, 8 Mar 2023 10:18:49 +0800 Subject: [PATCH 7/7] =?UTF-8?q?=E9=97=AB=E9=9B=AA=E8=8E=B2=E7=9A=84?= =?UTF-8?q?=E4=BD=9C=E4=B8=9A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...6 \345\255\220\346\237\245\350\257\242.md" | 167 ------------------ 1 file changed, 167 deletions(-) diff --git "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" index dbbeaa5..e69de29 100644 --- "a/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" +++ "b/37 \351\227\253\351\233\252\350\216\262/20230306 \345\255\220\346\237\245\350\257\242.md" @@ -1,167 +0,0 @@ -# 1.笔记 - -### 什么子查询 - --- 嵌套在其它SQL语句中的select语句 --- 子查询通常在外层语句之前优先执行，所以要用（）包括起来 --- 子查询的结果，一般作为外层语句的条件，数据源等 - -select ① from ③ where ②; - -### 形式一,select后面嵌套子查询 - -where 后面不支持聚合函数和别名，having支持聚合也支持别名 - -### 形式二，在where/having 后面做条件 - -当子查询放在where 、 having 后面当条件用是，有几种情况 - ① 单列单个值，可以直接用>,<,<=...!=，这些比较运算符 - ② 单列多个值，要用in,not in 这种集合的比较 - ③ 单列多个值，可以用>,<,<=...!=，比较运算符，搭配any,all 这些关键字，一起使用 - - - - - -### 形式三，在from后面,形成一个临时表，必须加一个别名 - -子查询的结果： -单列单个值：可以放在select 后，也可以放where/having之后 -单列多个值：where后，或having后 ，不用直接用<,=,>= 这种单纯的比较运算符。但可以用搭配any(任意一个),all(所有的)等关键字一起使用。还可以用in,not in这种表达式 - -多列时，只能当临时表来表用，放在from后面，而且必须，给他取个别名 - -# 2.作业 - -```mysql -create database yxll charset utf8; -use yxll; -create table stuinfo( -stuNO varchar(6) , -stuName varchar(6), -stuSex varchar(4), -stuAge varchar(4) , -stuAddress varchar(10), -stuSeat varchar(4) -); -desc stuinfo; -INSERT into stuinfo values('s2501','张秋利','男',20,'美国硅谷',1), - ('s2502','李斯才','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); - select *from stuinfo; - - -create table stuExam( -examNO varchar(3), -stuNO varchar(6), -writtenExam varchar(4), -labExam varchar(4) -); -desc stuExam; -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'); - -select *from stuExam ; - -create table stuMarks( -examNO varchar(3), -stuID varchar(6), -score varchar(4) -); -desc stuMarks; -INSERT into stuMarks values('1','s2501','88'), - ('2','s2502','92'), - ('3','s2503','53'), - ('4','s2504','60'), - ('5','s2505','99'), - ('6','s2506','82'); - - -select *from 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 * 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 max(score) from stuMarks; - SELECT stuinfo.stuNO, stuName, stuSex, (SELECT max(score) from stuMarks ) from stuinfo left join stuMarks on stuinfo.stuNO=stuMarks.stuID ; - - --- 3.查询出每个学生的学号，姓名，性别和考试平均分（stuExam） -SELECT (labExam+writtenExam)/2 from stuExam ; -SELECT stuinfo.stuNO, stuName, stuSex,(SELECT (labExam+writtenExam)/2 ) from stuinfo left join stuExam on stuinfo.stuNO=stuExam.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; -select * from (select * from stuinfo where stuage>=20) a where stusex='男'; - --- 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 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 stuinfo left join stuMarks on stuinfo.stuNO=stuMarks.stuID where score>=60; --- - -select * from stuinfo a INNER JOIN stumarks b on a.stuNo = b.stuID where a.stuNo != (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 * FROM stuinfo a inner join stumarks b on a.stuNo = b.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 * FROM stuinfo a inner join stumarks b on a.stuNo = b.stuID where 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 stuinfo inner join stuMarks on stuinfo.stuNO=stuMarks.stuID where stuMarks.score>90; --- - --- 10.查询出平均成绩在80分以上的学生的基本信息（stuExam） - -SELECT * from stuexam where stuexam.score >((labExam+writtenExam)/2 ); --- - -select * from stuinfo where stuno = (select stuno from stuexam where (writtenExam+labExam)/2>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 stuExam b on a.stuNo = b.stuNo where writtenExam>(select writtenExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')) AND labExam>(select labExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')); - --- 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 stuExam b on a.stuNo = b.stuNo where writtenExam>(select writtenExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')) OR labExam>(select labExam from stuExam where stuNo=(select stuNo from stuinfo where stuname='张秋利')); - --- 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 stuSex='女'and stuage>all(SELECT 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>any(SELECT stuage from stuinfo where stuSex='男'); - - -``` - -- Gitee