Mysql中触发器的使用
概念 触发器是一种特殊的事务,它监听增删改操作,并触发增删改操作。主要是用来处理一些比较复杂的业务逻辑以保证数据的联动性。其包含了四要素:1.监视地点(table) 2.监视事件(insert/update/delete) 3.触发时间(after/before) 4.触发事件(insert/update/d
概念
触发器是一种特殊的事务,它监听增删改操作,并触发增删改操作。主要是用来处理一些比较复杂的业务逻辑以保证数据的联动性。其包含了四要素:1.监视地点(table) 2.监视事件(insert/update/delete) 3.触发时间(after/before) 4.触发事件(insert/update/delete)
语法
<code class=" hljs sql"> <span class="hljs-operator"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TRIGGER</span> <span class="hljs-string">'触发器名称'</span> <span class="hljs-string">'触发时间(after|before)'</span> <span class="hljs-string">'监听的事情(insert|update|delete) '</span> <span class="hljs-keyword">ON</span> <span class="hljs-string">'触发地点'</span> <span class="hljs-keyword">FOR</span> <span class="hljs-keyword">EACH</span> <span class="hljs-keyword">ROW</span> <span class="hljs-keyword">BEGIN</span> sql1;</span> sql2; sql3; <span class="hljs-operator"><span class="hljs-keyword">END</span>$</span></code>
FOR EACH ROW 用来标识触发器的类型,因为Mysql支持行级别的触发器,不支持语句触发器,故只能使用FOR EACH ROW 。因为触发器中使用’;’区分多个事件语句,故需要重新定义定界符。
实例
修改定界符为$
创建触发器
查看触发器
执行操作之前
t4表数据如下
t3表数据如下
执行相应的操作之后

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