在MySQL中执行DELETE操作后触发触发器
mysqlmysqli database
使用 AFTER DELETE 在执行 DELETE 操作后触发触发器。以下是语法 −
DELIMITER // CREATE TRIGGER yourTriggerName AFTER DELETE ON yourTableName FOR EACH ROW BEGIN yourStatement1, . . N END; //
首先我们创建一个表 −
mysql> create table DemoTable(Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,FirstName varchar(100)); Query OK, 0 rows affected (0.62 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(FirstName) values('John');
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable(FirstName) values('Mike');
Query OK, 1 row affected (0.12 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable;
这将产生以下输出 −
+----+-----------+ | Id | FirstName | +----+-----------+ | 1 | John | | 2 | Mike | +----+-----------+ 2 rows in set (0.00 sec)
以下是创建触发器并使用 AFTER DELETE 的查询 −
mysql> DELIMITER // mysql> CREATE TRIGGER history_of_Table AFTER DELETE ON DemoTable FOR EACH ROW BEGIN SELECT USER() INTO @userName; SELECT NOW() INTO @deleteDatetime; END; // Query OK, 0 rows affected (0.18 sec) mysql> DELIMITER ;
要检查触发器是否工作，请从表中删除第一条记录 −
mysql> delete from DemoTable where Id=1; Query OK, 1 row affected (0.26 sec)
Above, we have deleted first record from the table. This means trigger must be active after DELETE command is used −
mysql> select @userName;
这将产生以下输出 −
+----------------+ | @userName | +----------------+ | root@localhost | +----------------+ 1 row in set (0.00 sec)
每当触发器工作时，它都会显示当前时间 −
mysql> select @deleteDatetime;
这将产生以下输出 −
+---------------------+ | @deleteDatetime | +---------------------+ | 2019-07-09 21:06:31 | +---------------------+ 1 row in set (0.00 sec)
