CREATE TABLE carts (
    id CHAR(36) PRIMARY KEY,
    customer_id CHAR(36) DEFAULT NULL,
    session_id VARCHAR(255) DEFAULT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    FOREIGN KEY (customer_id) REFERENCES customers(id) ON DELETE CASCADE,
    INDEX idx_customer_id (customer_id),
    INDEX idx_session_id (session_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;