触发器能同步更新数据,即一张表的更新、删除、插入等操作能自动触发该表或者其它表数据的更新删除同步。
这点就很有优势,有了触发器我们就不需要再在代码里面实现数据表同步,而让数据库自动完成。
举例如下:
1. 创建OTA升级包表如下
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. 创建升级包对应的设备号白名单表如下
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. 创建一个触发器,当删除升级包后,自动删除设备白名单表对应的升级包设备白名单记录
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;