mysql修改字段自增报错

ERROR 1068 (42000): Multiple primary key defined

ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key

-- 创建表
CREATE TABLE users (
    id INT,
    name VARCHAR(255),
    email VARCHAR(255)
);

-- 插入数据
INSERT INTO users (name, email) VALUES ('Alice', 'alice@example.com');
INSERT INTO users (name, email) VALUES ('Bob', 'bob@example.com');

-- 修改字段为自增并设置为主键
ALTER TABLE users MODIFY id INT AUTO_INCREMENT PRIMARY KEY;