mysql不能建外键约束

CREATE TABLE parent (
    id INT PRIMARY KEY,
    name VARCHAR(255)
);

CREATE TABLE child (
    id INT PRIMARY KEY,
    parent_id INT,
    FOREIGN KEY (parent_id) REFERENCES parent(id)
);

CREATE TABLE parent (
    id INT PRIMARY KEY,
    name VARCHAR(255)
) ENGINE=InnoDB;

CREATE TABLE child (
    id INT PRIMARY KEY,
    parent_id INT,
    FOREIGN KEY (parent_id) REFERENCES parent(id)
) ENGINE=InnoDB;

-- 确保parent表中有对应的数据
INSERT INTO parent (id, name) VALUES (1, 'Parent1');

-- 然后创建child表并添加外键约束
CREATE TABLE child (
    id INT PRIMARY KEY,
    parent_id INT,
    FOREIGN KEY (parent_id) REFERENCES parent(id)
);

GRANT ALL PRIVILEGES ON database_name.* TO 'username'@'localhost';
FLUSH PRIVILEGES;