MySQL中REPLACE INTO语句原理、用法与最佳实践

REPLACE [INTO] table_name [(column_list)]
VALUES (value_list)
-- 或
REPLACE [INTO] table_name [(column_list)]
SELECT ...

-- 从临时表同步数据到正式表
REPLACE INTO products (id, name, price, stock)
SELECT id, name, price, stock FROM temp_products;

-- 更新系统配置表
REPLACE INTO system_config (config_key, config_value, update_time)
VALUES ('max_connections', '100', NOW());

-- 更新缓存表数据
REPLACE INTO user_cache (user_id, username, last_active)
VALUES (123, 'john_doe', '2023-05-20 10:00:00');

-- 创建测试表
CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(50) UNIQUE,
    email VARCHAR(100),
    login_count INT DEFAULT 0
);

-- 第一次执行：插入新记录
REPLACE INTO users (username, email, login_count)
VALUES ('john_doe', 'john@example.com', 1);

-- 第二次执行（相同username）：替换原有记录
REPLACE INTO users (username, email, login_count)
VALUES ('john_doe', 'john.new@example.com', 2);

-- 创建有复合唯一键的表
CREATE TABLE user_roles (
    user_id INT,
    role_id INT,
    grant_date DATETIME,
    PRIMARY KEY (user_id, role_id)
);

-- 使用REPLACE INTO
REPLACE INTO user_roles (user_id, role_id, grant_date)
VALUES (1001, 2, NOW());

-- 从一个表同步数据到另一个表
REPLACE INTO target_table (id, col1, col2)
SELECT id, col1, col2 FROM source_table
WHERE update_time > '2023-01-01';

START TRANSACTION;
REPLACE INTO important_table (...) VALUES (...);
-- 检查影响行数或其他条件
COMMIT; -- 或 ROLLBACK

# Python 批量操作示例
def batch_replace(table, data_list, batch_size=1000):
    conn = get_db_connection()
    try:
        with conn.cursor() as cursor:
            for i in range(0, len(data_list), batch_size):
                batch = data_list[i:i+batch_size]
                values = ", ".join([
                    f"({pymysql.escape_string(str(item['id']))}, "
                    f"'{pymysql.escape_string(item['name'])}')"
                    for item in batch
                ])
                sql = f"REPLACE INTO {table} (id, name) VALUES {values}"
                cursor.execute(sql)
        conn.commit()
    except Exception as e:
        conn.rollback()
        raise e
    finally:
        conn.close()

-- 方法1：INSERT IGNORE（忽略错误）
INSERT IGNORE INTO table (...) VALUES (...);

-- 方法2：ON DUPLICATE KEY UPDATE（更新特定字段）
INSERT INTO table (...) VALUES (...)
ON DUPLICATE KEY UPDATE update_time = NOW();