mysql怎么建联合主键

CREATE TABLE orders (
    order_id INT NOT NULL,
    customer_id INT NOT NULL,
    order_date DATE,
    total_amount DECIMAL(10, 2),
    PRIMARY KEY (order_id, customer_id)
);

CREATE TABLE orders (
    order_id INT NOT NULL,
    customer_id INT NOT NULL,
    order_date DATE,
    total_amount DECIMAL(10, 2),
    PRIMARY KEY (order_id, customer_id)
);

-- 创建新表结构
CREATE TABLE orders_new (
    order_id INT NOT NULL,
    customer_id INT NOT NULL,
    order_date DATE,
    total_amount DECIMAL(10, 2),
    PRIMARY KEY (order_id, customer_id)
);

-- 将数据从旧表导入新表
INSERT INTO orders_new (order_id, customer_id, order_date, total_amount)
SELECT order_id, customer_id, order_date, total_amount FROM orders;

-- 删除旧表
DROP TABLE orders;

-- 重命名新表
RENAME TABLE orders_new TO orders;