触发器用CREATE TRIGGER 语句创建,一条伪代码如下: CREATE TRIGGER newType AFTER INSERT ON ms_articletype for each row select 'Product Added'; Error Code: 1415. Not allowed to return a result set from a trigger 1. 2. 创建一个触发器需要给出4条信息: 唯一的触发器名 newType 触发器关联的表 m...
计算input_expression,然后按指定顺序对每个 WHEN 子句的 input_expression = when_expression 进行计算。 返回第一个取值为 TRUE 的 (input_expression = when_expression) 的 result_expression。 如果没有取值为 TRUE 的 input_expression = when_expression,则当指定 ELSE 子句时 SQL Server 将返回 else_result_...
You may find theMySQL User Forumshelpful when working with triggers. For answers to commonly asked questions regarding triggers in MySQL, seeSection A.5, “MySQL 8.0 FAQ: Triggers”. There are some restrictions on the use of triggers; seeSection 27.8, “Restrictions on Stored Programs”. ...
END $ DELIMITER ; -- 创建一个触发器 CREATE TRIGGER 触发器名称 {BEFORE | AFTER} {INSERT | UPDATE | DELETE} ON 表名 FOR EACH ROW -- 触发器的逻辑(代码块); -- --- 用户变量与局部变量 --- -- 定义、修改用户变量 set @变量名称 = 变量值; -- 查询用户变量 select @变量名称; -- 定义...
在"TRIGGER"中,用于定义触发器的条件。触发器是一种特殊的存储过程,在插入、更新或删除表中的数据时自动触发。 例如: CREATE TRIGGER trigger_name BEFORE/AFTER INSERT/UPDATE/DELETE ON table_name FOR EACH ROW WHEN condition BEGIN -- 触发器的操作 END; 复制代码 总之,"WHEN"关键字的作用是帮助MySQL判断条...
CREATE TABLE test_trigger_log ( id INT PRIMARY KEY AUTO_INCREMENT, t_log VARCHAR(30) ); 2、创建触发器:创建名称为before_insert的触发器,向test_trigger数据表插入数据之前,向test_trigger_log数据表中插入before_insert的日志信息。 DELIMITER // ...
Triggers are often used to maintain the integrity of data across tables of an application. When a user on a website makes a purchase, for example, the first action that occurs in the database may be that a credit is inserted into an accounting table. ...
you can also change its value withSET NEW.col_name=valueif you have theUPDATEprivilege for it. This means you can use a trigger to modify the values to be inserted into a new row or used to update a row. (Such aSETstatement has no effect in anAFTERtrigger because the row change wil...
I would like to know if can i insert,update or delete data into replicated table using a trigger. For example: When i insert data into Table_A on master server, automatically the same data is inserted into Table_A of my slave server, but when i use a trigger to insert data into Tabl...
When a trigger is activated (by a user who has privileges to execute INSERT, UPDATE, or DELETE statements for the table associated with the trigger), trigger execution requires that the user who defined the trigger still have the TRIGGER privilege. ...