4）DML操作
DML操作：Data Manipulation Language，数据操纵语言；包含insert、update、delete操作；
1、单行插入数据格式：
insert into 表名【字段列表】 values(值列表)；向教师表插入：
insert into teacher values('001','李老师', '1110000000');
insert into teacher(teacher_no, teacher_name,teacher_contact) values('002','王老师','1110000001');
insert into teacher(teacher_name,teahcer_no,teacher_contact) values('孙老师','003','1110000002');
向班级表插入：
insert into classes values(null,'2023自动化1班','自动化');
insert into classes(class_name,department_name) values('2023自动化2班','自动化');
insert into classes values(3,'2023自动化3班','自动化');
向课程表插入：
insert into course values(null,'c语言',default,'暂无','已审核','001');
或者 insert into course (course_name,description,status,teacher_no) values('c语言','暂无','已审核','001');
insert into course values(null,'MySQL',150,'暂无','已审核','002');
insert into course values(nuil,'c++',230,'暂无','已审核','003');
2、批量插入多行数据格式:
insert into 表名【字段列表】 values(值列表1),(值列表2),..(值列表n);向学生表批量插入：
insert into student values('2023001','张三','2220000000',1),('2023002','李四','2220000001',1),('2023003','王五','2220000002',3),('2023004','马六','2220000003',2),('2023005','田七','2220000004',2);
3、查询插入多行数据：
insert into 目标表名【字段列表1】 select（字段列表2） from 源表 where 条件表达式；先创建一个新表：
create table stu1 like student;
insert into stu1 select * from student;
select * from stu1;
4、update语句：
update 表名 set 字段名1=值1[,字段名2=值2] ;新建一个表，做测试：
create table exam (
stu_no int auto_increment primary key,
exam_score tinyint unsigned,
regular_score tinyint unsigned
);
insert into exam values(null,80,85),(null,99,90),(null,65,70),(null,52,null),(null,20,null);
update exam setexam_score=exam_score+5; update exam set exam_score=100 where exam_score>=100; update exam set exam_score=60 where exam_score>=55 and exam_score
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