MySQL reports an error can't create table 'demo01 tb_ Student‘ (errno: 150)*

mysql An error is reported when adding a foreign key 150

Tips ：mysql An error is reported when adding a foreign key , But the type of foreign keys is the same , And this field also exists in another table
Wrong content ：Can’t create table ‘demo01.tb_Student’ (errno: 150)

Introduction to foreign key usage ：

CONSTRAINT Fk_Class_Student FOREIGN KEY(classId) references  tb_class(classId)
CONSTRAINT  Constraint name  FOREIGN KEY( Foreign key name ) references   The table name to be associated with the foreign key ( Field name )

CREATE TABLE tb_class(
classId int PRIMARY KEY AUTO_Increment,
ClassName varchar(20) not null
);


CREATE TABLE tb_Student(
StudentId int primary key Auto_increment,
StudentName varchar(20),
classId  int not NULL,
CONSTRAINT Fk_Class_Student FOREIGN KEY(classId) references  tb_class(classId)
)

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Solution ：

Tips ： Creating tb_Student Add after when ENGINE = MYISAM;

CREATE TABLE tb_class(
classId int PRIMARY KEY AUTO_Increment,
ClassName varchar(20) not null
);


CREATE TABLE tb_Student(
StudentId int primary key Auto_increment,
StudentName varchar(20),
classId  int not NULL,
CONSTRAINT Fk_Class_Student FOREIGN KEY(classId) references  tb_class(classId)
)ENGINE = MYISAM;