建表、数据插入代码：
#新建学生表 drop table if exists student; create table student( sno varchar(20) not null primary key comment '学号', sname varchar(20) not null comment '学生姓名', ssex varchar(20) not null comment '学生性别', sbirthday Datetime comment '学生出生年月', class varchar(20) comment '学生所在班级' ); #给学生表中插入数据 insert into student values( '108','曾华','男','1977-09-01','95033'),( '105','匡明','男','1975-10-02','95031'),( '107','王丽','女','1976-01-23','95033'),( '101','李军','男','1976-02-20','95033'),( '109','王芳','女','1975-02-10','95031'),( '103','陆君','男','1974-06-03','95031'); #新建课程表 drop table if exists course; create table course( cno varchar (20) not null primary key comment '课程号', cname varchar (20) not null comment '课程名称', tno varchar (20) not null comment '教工编号' ); #给课程表中插入数据 insert into course values ('3-105','计算机导','825'), ('3-245','操作系统','804'), ('6-166','数字电路','856'), ('9-888','高等数学','831'); #新建成绩表 drop table if exists score; create table score( sno varchar (20) not null comment '学号', cno varchar (20) not null comment '课程号', degree Decimal(4,1) comment '成绩', primary key(sno,cno) ); #给成绩表中插入数据 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); #新建教师表 drop table if exists teacher; create table teacher( tno varchar (20) not null primary key comment '教工编号', tname varchar (20) not null comment '教工姓名', tsex varchar (20) not null comment '教工性别', tbirthday datetime comment '教工出生年月', prof varchar (20) comment '职称', depart varchar (20) not null comment '教工所在部门' ); #给教师表中插入数据 insert into teacher values ('804','李诚','男','1958-12-02','副教授','计算机'), ('856','张旭','男','1969-03-12','讲师','电子工程'), ('825','王萍','女','1972-05-05','助教','计算机系'), ('831','刘冰','女','1977-08-14','助教','电子工程');
开始查询：
#like：姓王的 select * from teacher where tname like '王%'; #like：第二个字是冰的 select * from teacher where tname like '_冰%'; #1、 查询Student表中的所有记录的Sname、Ssex和Class列。 select sname,ssex,class from student; /*2、 查询教师所有的单位即不重复的Depart列。 all：允许出现——默认不写就是All（允许的）。 distinct：不允许出现——就是所谓的“消除重复行”。*/ select distinct depart from teacher ; select count(distinct depart) from teacher; #3、 查询Student表的所有记录。 select * from student; #4、 查询Score表中成绩在60到80之间的所有记录。 select * from score where degree >= 60 and degree <= 80; select * from score where degree between 60 and 80; #5、 查询Score表中成绩为85，86或88的记录。 select * from score where degree = 85 or degree = 86 or degree = 88; select * from score where degree in(85,86,88); #6、 查询Student表中“95031”班或性别为“女”的同学记录。 select * from student where class = '95031' or ssex = '女'; #7、 以Class降序查询Student表的所有记录。 select * from student order by class desc; # 8、以Cno升序、Degree降序查询Score表的所有记录。 #order by 字段名（默认升序）；desc：降序 select * from score order by cno,degree desc;
1 #9、查询“95031”班的学生人数。 2 select *,count(*) from student where class = '95031'; 3 #10、 查询Score表中的最高分的学生学号和课程号。（子查询或者排序） 4 select sno,cno from score where degree = (select max(degree) from score); 5 # 11、查询每门课的平均成绩。 6 select cno,avg(degree) as avgdg from score group by cno; 7 #12、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。 8 select cno,avg(degree),count(sno) as cotsno from score group by cno having cotsno > 5 and cno like '3%'; 9 #13、查询分数大于70，小于90的Sno列。 10 select sno from score where degree between 70 and 90; 11 #14、查询所有学生的Sname、Cno和Degree列。 12 select sname,cno,degree from student join score on student.sno = score.sno; 13 #15、查询所有学生的Sno、Cname和Degree列。 14 select sno,cname,degree from score join course on score.cno = course.cno; 15 #16、查询所有学生的Sname、Cname和Degree列。 16 select sname,cname,degree from student join score on student.sno = score.sno join course on score.cno = course.cno; 17 #17、 查询“95033”班学生的平均分。 18 select class,avg(degree) from student join score on student.sno = score.sno where class = '95033'; 19 #select class,avg(degree) from student,score where class = '95033' and student.sno = score.sno; 20 #select class,avg(degree) from (select degree,class from student as s join score as c on s.sno = c.sno) as class1 where class= '95033'; 21 # 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。 22 select * from score where cno = '3-105' and degree>(select degree from score where sno='109' and cno ='3-105'); 23 select * from student where sno in(select sno from score where cno = '3-105') and (select degree from score) > (select degree from score where sno='109' and cno = '3-105') ; 24 #20、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。 25 #去除每门课程的最高分 26 #select * from score a where sno in (select sno from score group by sno having count(*)>1 ) and degree not in (select max(degree) from score b where b.cno = a.cno) ; 27 #去除所有课程的最高分92分 28 #select * from score a where sno in (select sno from score group by sno having count(*)>1 ) and degree not in (select max(degree) from score a where sno in (select sno from score group by sno having count(*)>1 )); 29 /*select * from score a where degree in (select max(degree) from score b where b.sno = a.sno) ; 30 select max(Score.degree) from Score join (select degree,cno from Score) as aaa on score.cno = aaa.cno;*/
#21、 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 sno='109' and cno ='3-105'); #22、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 sno <> '107' and year(sbirthday) = (select year(sbirthday) from student where sno = '107'); #23、查询“张旭“教师任课的学生成绩（姓名）。 #1、从成绩表 查询学生成绩 #2、条件是这个课程是 “张旭“教师任课 #A)从老师表 中查名字叫 张旭 编号 #B)根据老师编号 在课程表中找到对应的 课程号 ①select sname,degree from score join course on score.cno = course.cno join teacher on teacher.tno = course.tno join student on score.sno = student.sno where tname = '张旭'; ②select sname,aaa.degree from student join (select sno,degree from score where cno = (select cno from course where tno = (select tno from teacher where tname = '张旭'))) as aaa on student.sno = aaa.sno; #查询考计算机导论的学生成绩 #查询 所有的列/字段 从 成绩表(score) 条件是 #课程编号是：课程表(course)中 课程名(cname)称为计算机导论 的课程编号 #课程表(course)中 课程名(cname)称为计算机导论 的课程编号===3-105 #查询 所有的列/字段 从 成绩表(score) 条件是 课程编号是：3-105 select cname,degree from score join course on score.cno = course.cno where course.cno = '3-105'; #查询李诚老师教的课程名称 select cname,tname from course join teacher on teacher.tno = course.tno where(and) tname = '李诚'; #教高等数学的老师是哪个系的 select tname,cname,depart from teacher join course on teacher.tno = course.tno where cname = '高等数学'; #24、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 where tno in (select tno from course cu where (select aaa.cno from (select sc.cno,count(sno) from score sc group by cno having count(sno) > 5) as aaa where cu.cno=aaa.cno)) ; select tname from teacher where tno in (select tno from course where cno in(select cno from score group by cno having count(*)>5)); #25、查询95033班和95031班全体学生的记录。 select * from student where class = '95033' or class = '95031'; #26、 查询存在有85分以上成绩的课程Cno. select cno,max(degree) from score group by cno having max(degree) > 85; #27、查询出“计算机系“教师所教课程的成绩表。 select * from score where cno in(select cno from course join teacher on course.tno = teacher.tno where depart = '计算机系'); #29、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 > (select min(degree) from score where cno = '3-245') order by degree desc; #30、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 cno,sno,degree from score where cno = '3-105' and degree > (select max(degree) from score where cno = '3-245'); #31、 查询所有教师和同学的name、sex和birthday. select sname as name,ssex as sex,sbirthday as birthday from student union select tname,tsex,tbirthday from teacher; #32、查询所有“女”教师和“女”同学的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';
#36、查询至少有2名男生的班号：多字段分组 select class from student group by class,ssex having ssex = '男' and count(*) >= 2; #37、查询Student表中不姓“王”的同学记录。 select * from student where sname not like '王%'; #38、查询Student表中每个学生的姓名和年龄。 select sname,year(now()) - year(sbirthday) as age from student; #39、查询Student表中最大和最小的Sbirthday日期值。 #错误：min()..不能直接使用，无效的方法。select sbirthday from student where sbirthday in(min(sbirthday),max(sbirthday)); select sbirthday from student where sbirthday = (select max(sbirthday) from student) or sbirthday = (select min(sbirthday) from student); select min(sbirthday),max(sbirthday) from student; #40、以班号和年龄从大到小的顺序查询Student表中的全部记录。 #select *, year(now()) - year(sbirthday) as age from student order by class desc,age desc; select * from student order by class desc,sbirthday; #41、查询“男”教师及其所上的课程。 select teacher.*,cname from teacher join course on teacher.tno = course.tno and tsex = '男'; #42、查询最高分同学的Sno、Cno和Degree列。 select * from score where degree = (select max(degree) from score); #43、查询和“李军”同性别的所有同学的Sname. select sname,ssex from student where ssex = (select ssex from student where sname = '李军') and sname <> '李军'; #44、查询和“李军”同性别并同班的同学Sname. select sname,ssex,class from student where ssex = (select ssex from student where sname = '李军' ) and class = (select class from student where sname = '李军' ) and sname <> '李军'; #45、查询所有选修“计算机导论”课程的“男”同学的成绩表。 select * from score where cno in (select cno from course where cname = '计算机导')and sno in(select sno from student where ssex = '男');