mysql 删除有外键的数据

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

CREATE TABLE child (
    id INT PRIMARY KEY,
    parent_id INT,
    name VARCHAR(255),
    FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE
);

-- 删除父表中的记录
DELETE FROM parent WHERE id = 1;

-- 删除子表中的记录
DELETE FROM child WHERE parent_id = 1;

-- 删除父表中的记录
DELETE FROM parent WHERE id = 1;

CREATE TABLE child (
    id INT PRIMARY KEY,
    parent_id INT,
    name VARCHAR(255),
    FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE SET NULL
);

-- 删除父表中的记录
DELETE FROM parent WHERE id = 1;

-- 创建父表
CREATE TABLE parent (
    id INT PRIMARY KEY,
    name VARCHAR(255)
);

-- 创建子表，并设置外键约束
CREATE TABLE child (
    id INT PRIMARY KEY,
    parent_id INT,
    name VARCHAR(255),
    FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE
);

-- 插入数据
INSERT INTO parent (id, name) VALUES (1, 'Parent 1');
INSERT INTO child (id, parent_id, name) VALUES (1, 1, 'Child 1');

-- 删除父表中的记录
DELETE FROM parent WHERE id = 1;