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Fire trigger after the DELETE operation is executed in MySQL
Use AFTER DELETE to fire trigger after the DELETE operation is executed. Following is the syntax −
DELIMITER // CREATE TRIGGER yourTriggerName AFTER DELETE ON yourTableName FOR EACH ROW BEGIN yourStatement1, . . N END; //
Let us first create a table −
mysql> create table DemoTable(Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,FirstName varchar(100)); Query OK, 0 rows affected (0.62 sec)
Insert some records in the table using insert command −
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)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+----+-----------+ | Id | FirstName | +----+-----------+ | 1 | John | | 2 | Mike | +----+-----------+ 2 rows in set (0.00 sec)
Following is the query to create trigger and use AFTER DELETE as well −
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 ;
To check the trigger is working or not, delete first record from the table −
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;
This will produce the following output −
+----------------+ | @userName | +----------------+ | root@localhost | +----------------+ 1 row in set (0.00 sec)
It displays the current time whenever trigger works −
mysql> select @deleteDatetime;
This will produce the following output −
+---------------------+ | @deleteDatetime | +---------------------+ | 2019-07-09 21:06:31 | +---------------------+ 1 row in set (0.00 sec)
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