create database two20210610 default charset=utf8;
use two20210610;
CREATE TABLE studentinfo (
StudentID char(10) DEFAULT NULL,
StudentName varchar(20) DEFAULT NULL,
Gender varchar(2) DEFAULT NULL,
Birthday date DEFAULT NULL,
ClassID int(4) DEFAULT NULL,
BeginYear year(4) DEFAULT NULL,
Phone varchar(11) DEFAULT NULL,
Province varchar(20) DEFAULT NULL,
City varchar(20) DEFAULT NULL,
Email varchar(50) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
create table teacher (
id int,
teachername VARCHAR(10),
hiredate DATE,
gender char
);
create table classinfo (
id int, # 班级编号
classname varchar(10),
gradeid int, # 年级编号
beginyear varchar(10) # 开始年份
);
create table subject (
id int ,
subjectname varchar(10),
teacherid int
);
create table exam (
id int,
exam int,
subjectid int,
studentid int,
remark varchar(10) # 备注
);
create table grade(
id int ,
gradename varchar(10),
major varchar(20)
);
INSERT INTO two20210610.classinfo(id, classname, gradeid, beginyear) VALUES (2001, '20级1班', 20, '2020');
INSERT INTO two20210610.classinfo(id, classname, gradeid, beginyear) VALUES (2002, '20级2班', 20, '2020');
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (1, 98, 101, 1, '无');
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (2, 89, 102, 1, NULL);
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (3, 79, 103, 1, '');
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (4, 96, 104, 1, NULL);
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (5, 85, 101, 2, NULL);
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (6, 89, 102, 2, NULL);
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (7, 79, 103, 2, NULL);
INSERT INTO two20210610.exam(id, exam, subjectid, studentid, remark) VALUES (8, 83, 104, 2, NULL);
INSERT INTO two20210610.grade(id, gradename, major) VALUES (20, '20级', '软件技术');
INSERT INTO two20210610.studentinfo(StudentID, StudentName, Gender, Birthday, ClassID, BeginYear, Phone, Province, City, Email) VALUES ('1', '张无忌', '男', '2021-06-10', 2001, 2020, '13012340001', '河南', '许昌', 'zwj@qq.com');
INSERT INTO two20210610.studentinfo(StudentID, StudentName, Gender, Birthday, ClassID, BeginYear, Phone, Province, City, Email) VALUES ('2', '张铁牛', '男', '2021-06-16', 2001, 2020, '13012340002', '河南', '许昌', 'ztn@qq.com');
INSERT INTO two20210610.studentinfo(StudentID, StudentName, Gender, Birthday, ClassID, BeginYear, Phone, Province, City, Email) VALUES ('3', '林平之', '男', '2021-06-15', 2001, 2020, '13012340003', '河南', '安阳', 'lpz@qq.com');
INSERT INTO two20210610.studentinfo(StudentID, StudentName, Gender, Birthday, ClassID, BeginYear, Phone, Province, City, Email) VALUES ('4', '令狐冲', '男', '2021-06-08', 2002, 2019, '13012340004', '河南', '濮阳', 'lhc@qq.com');
INSERT INTO two20210610.studentinfo(StudentID, StudentName, Gender, Birthday, ClassID, BeginYear, Phone, Province, City, Email) VALUES ('5', '岳灵珊', '女', '2021-06-02', 2002, 2019, '13012340005', '河南', '南阳', 'yls@qq.com');
INSERT INTO two20210610.subject(id, subjectname, teacherid) VALUES (101, 'mysql', 201);
INSERT INTO two20210610.subject(id, subjectname, teacherid) VALUES (102, 'java基础', 201);
INSERT INTO two20210610.subject(id, subjectname, teacherid) VALUES (103, '面向对象', 202);
INSERT INTO two20210610.subject(id, subjectname, teacherid) VALUES (104, '网页设计', 202);
INSERT INTO two20210610.teacher(id, teachername, hiredate, gender) VALUES (201, 'hys', '2021-06-04', '男');
INSERT INTO two20210610.teacher(id, teachername, hiredate, gender) VALUES (202, 'dj', '2021-06-01', '女');
-- 子查询 用子查询实现，查询出学生“林平之”的同班同学
1 找到林平之 的班级
2 查同班同学
找到林平之 的班级
select classid from studentinfo where studentname='林平之';
根据班级查询同班同学信息
select * from studentinfo where classid='2001';
合并
select * from studentinfo where classid=(select classid from studentinfo where studentname='林平之');
查询《mysql》考试成绩刚好等于90分的学生名单
-- 1 需要查询学生名单 在studentinfo
-- 2 科目是mysql 在subject表中 id
-- 3 成绩为98 在exam表中 subjectid studentid
-- 方法一
select studentname from studentinfo S inner join exam e on S.StudentID=e.studentid inner join subject on e.subjectid=subject.id where subject.subjectname='mysql' and e.exam=98;
-- 方法二
select studentname '学生姓名' from studentinfo s where
s.StudentID=(select id from exam where
exam=98 and subjectid=(select id from subject where subjectname='mysql') )
-- 更新令狐冲的网页设计成绩+5分
-- 找到......成绩
update exam set exam = exam + 5 where subjectid = ?
-- 找到mysql课程的id
select id from subject where subjectname='网页设计'
-- 根据名字找id
select id from teacher where teachername='dj'
-- 融合
update exam set exam = exam + 5 where subjectid = (select id from subject where subjectname = '网页设计' and subject.teacherid = (select id from teacher where teachername='dj'
))
-- 删除张无忌的所有考试成绩
-- 1 找到张无忌地学生id
select studentid from studentinfo where studentname='张无忌'
-- 2 根据id在exam表中删除成绩
delete from exam where studentid=?
-- 合并
delete from exam where studentid=(select studentid from studentinfo where StudentName='张无忌');
-- 插入的子查询 把查询的结果作为内容 插入到新的数据
insert into studentinfo (select * from studentinfo where studentid=5);
查询《mysql》考试成绩刚好等于90分的学生名单
-- 1 需要查询学生名单 在studentinfo
-- 2 科目是mysql 在subject表中 id
-- 3 成绩为98 在exam表中 subjectid studentid
-- 方法一
select studentname from studentinfo S inner join exam e on S.StudentID=e.studentid inner join subject on e.subjectid=subject.id where subject.subjectname='mysql' and e.exam=85;
-- 方法二
select studentname '学生姓名' from studentinfo s where
s.StudentID in (select id from exam where
exam=85 and subjectid in (select id from subject where subjectname='mysql') )
-- 查询成绩中科目编号为2的考试成绩中是否存在不及格的学生
-- 是否存在不及格的学生
select studentID exam from exam where exam<80
-- 参加科目编号102的学生
where SubjectID=102
-- 学生编号和成绩全部查询显示出来
select StudentID,exam from exam
-- 融合
select StudentID,exam from exam where SubjectID=102 and exists (select StudentID from exam where exam<80);
-- 查询成绩比科目编号为1 的这门课的所有成绩都大的学生考试信息
-- 查询。。。学生考试信息
select * from exam where where ?
-- 成绩比科目编号为101的这门课程的所有成绩都大
all(select exam from exam where SubjectID=1)
-- 合并
select * from exam where exam > all(select exam from exam where subjectid=101);
