Detailed explanation of the foreign key constraint inspection method of closing child tables in MySQL (picture)

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Preparation:

Define a teacher table and a student table; reference the teacher table in the student table ID

create table teachers(teacherID int not null auto_increment primary key,teacherName varchar(8));
create table students(studentID int not null auto_increment primary key,teacherID int not null,studentName varchar(8),
constraint fk_students_teacherID foreign key (teacherId) references teachers(teacherId) on delete no action on update cascade);

Step one:

Insert a teacher

insert into teachers(teacherName) values('NameA');

insert into students(studentName,teacherID) values('NameB',100);--可以知道没有这个教师号、所以插入会出错。

Step 2:

insert into students(studentName,teacherID) values('NameB',100)；

Step 3:

set foreign_key_checks =1;

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