觸發器能同步更新數據,即一張表的更新、刪除、插入等操作能自動觸發該表或者其它表數據的更新刪除同步。
這點就很有優勢,有了觸發器我們就不需要再在代碼裏面實現數據表同步,而讓數據庫自動完成。
舉例如下:
1. 創建OTA升級包表如下
DROP TABLE IF EXISTS `darling_package`;
CREATE TABLE `darling_package` (
`package_id` int(32) NOT NULL AUTO_INCREMENT,
`project_id` int(32) NOT NULL,
`version_id` int(32) NOT NULL,
`create_time` datetime NOT NULL,
`package_size` int(32) NOT NULL,
`status` int(2) NOT NULL,
`package_path` varchar(255) NOT NULL,
`package_md5` varchar(255) NOT NULL,
`target_version` varchar(128),
PRIMARY KEY (package_id),
UNIQUE KEY `package_id` (`package_id`)
);
2. 創建升級包對應的設備號白名單表如下
DROP TABLE IF EXISTS `darling_package_whitelist`;
CREATE TABLE `darling_package_whitelist` (
`id` int(32) NOT NULL AUTO_INCREMENT,
`package_id` int(32) NOT NULL,
`device_number` varchar(255) NOT NULL UNIQUE,
PRIMARY KEY (id),
UNIQUE KEY `id` (`id`)
);
3. 創建一個觸發器,當刪除升級包後,自動刪除設備白名單表對應的升級包設備白名單記錄
DROP TRIGGER IF EXISTS t_delete_package;
CREATE TRIGGER t_delete_package
AFTER DELETE ON darling_package
FOR EACH ROW
delete from darling_package_whitelist where package_id=old.package_id;