CREATE TABLE `invoice_alert_log` (
  `id` INT NOT NULL AUTO_INCREMENT,
  `invoice_type` VARCHAR(20) NOT NULL,
  `invoice_id` INT NOT NULL,
  `alert_type` VARCHAR(20) NOT NULL,
  `sent_at` DATETIME(0) NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  UNIQUE KEY `invoice_type_invoice_id_alert_type` (`invoice_type`, `invoice_id`, `alert_type`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;