mysql触发器

• 时间点：before/after
• 触发事件： update/delete/insert
• 时间点+触发事件：构成一个完整的触发器的触发时机；
• 一个触发时机最多只能由1个Trigger：如 before-insert最多只能有1个触发器，如果需要多个，需要在1个Trigger内些sql Statement；

old和new

• insert：只有new关键字可以使用；
• update: new和old关键字都可以使用；
• delete: 只有old关键字可以使用；

完整语句

CREATE TABLE `capacity_pm` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT ‘自增主键‘,
  `pool_id` char(36) CHARACTER SET utf8 DEFAULT NULL COMMENT ‘资源池ID‘,
  `cluster_lv1` varchar(255) CHARACTER SET utf8 DEFAULT NULL COMMENT ‘集群分类‘,
  `cluster_lv2` varchar(255) CHARACTER SET utf8 DEFAULT NULL COMMENT ‘集群2级分类‘,
  `update_at` datetime DEFAULT CURRENT_TIMESTAMP COMMENT ‘更新或创建时间‘,
  `templete_id` varchar(255) CHARACTER SET utf8 NOT NULL COMMENT ‘模板ID‘,
  `templete_name` varchar(255) CHARACTER SET utf8 DEFAULT NULL COMMENT ‘模板名称‘,
  `templete_cpu_core` int(10) unsigned zerofill NOT NULL COMMENT ‘模板CPU核数‘,
  `templete_mem_size` double NOT NULL COMMENT ‘模板内存大小‘,
  `templete_disk_size` double NOT NULL COMMENT ‘模板磁盘大小‘,
  `host_total` int(11) unsigned zerofill DEFAULT NULL COMMENT ‘主机总数‘,
  `host_used` int(11) unsigned zerofill DEFAULT NULL COMMENT ‘主机已分配数量‘,
  `cpu_core_total` int(11) unsigned zerofill DEFAULT NULL COMMENT ‘cpu总核数‘,
  `cpu_core_free` int(11) DEFAULT NULL,
  `cpu_core_used` int(11) DEFAULT NULL COMMENT ‘cpu已分配数量‘,
  `cpu_core_util` double(10,3) DEFAULT NULL COMMENT ‘cpu核数使用占比‘,
  `mem_total` double DEFAULT NULL COMMENT ‘内存总空间‘,
  `mem_free` double DEFAULT NULL,
  `mem_used` double DEFAULT NULL,
  `mem_util` double DEFAULT NULL COMMENT ‘内存使用占比‘,
  `disk_total` double DEFAULT NULL,
  `disk_free` double DEFAULT NULL,
  `disk_used` double DEFAULT NULL,
  `disk_util` double DEFAULT NULL COMMENT ‘磁盘使用占比‘,
  PRIMARY KEY (`id`),
  UNIQUE KEY `idx_templete_all` (`pool_id`,`templete_id`) USING BTREE COMMENT ‘模块ID做完整索引‘
) ENGINE=InnoDB AUTO_INCREMENT=101 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

CREATE TRIGGER `pm_before_insert_trigger` BEFORE INSERT ON `capacity_pm` FOR EACH ROW begin
set new.cpu_core_total=new.host_total * new.templete_cpu_core;
set new.cpu_core_used=new.host_used * new.templete_cpu_core;
set new.cpu_core_free=new.cpu_core_total - new.cpu_core_used;
set new.cpu_core_util=new.cpu_core_used / new.cpu_core_total;
end;

CREATE TRIGGER `pm_before_update_trigger` BEFORE UPDATE ON `capacity_pm` FOR EACH ROW begin
set new.cpu_core_total=new.host_total * old.templete_cpu_core;
set new.cpu_core_used=new.host_used * old.templete_cpu_core;
set new.cpu_core_free=new.cpu_core_total - new.cpu_core_used;
set new.cpu_core_util=new.cpu_core_used / new.cpu_core_total;
end;

创建触发器的语句

CREATE TRIGGER `pm_before_insert_trigger` BEFORE INSERT ON `capacity_pm` FOR EACH ROW begin
set new.cpu_core_total=new.host_total * new.templete_cpu_core;
set new.cpu_core_used=new.host_used * new.templete_cpu_core;
set new.cpu_core_free=new.cpu_core_total - new.cpu_core_used;
set new.cpu_core_util=new.cpu_core_used / new.cpu_core_total;
end;

CREATE TRIGGER `pm_before_update_trigger` BEFORE UPDATE ON `capacity_pm` FOR EACH ROW begin
set new.cpu_core_total=new.host_total * old.templete_cpu_core;
set new.cpu_core_used=new.host_used * old.templete_cpu_core;
set new.cpu_core_free=new.cpu_core_total - new.cpu_core_used;
set new.cpu_core_util=new.cpu_core_used / new.cpu_core_total;
end;

参考

mysql5.6-trigger官网

原文地址：https://www.cnblogs.com/ssslinppp/p/8806635.html