Question

I’m using MySql 5.5 database and i have test1,test2,test3 and test4 databases.
test1 database have 3 tables(Student,Employee,Trainer).
test2 database have 3 tables(table1,table2,table3).
Now my Question is

How to apply TRIGGER for test1 database ? so hear the TRIGGER is applied for Student,Employee,Trainer tables.

Please give me solution.

Answer 1

The general syntax of CREATE TRIGGER is :
CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name FOR EACH ROW trigger_statement

in the following example we are updating the Salary column of Employee table before inserting any record in Emp table. Example :

mysql> SELECT * FROM Employee;

+—–+———+———-+——————-+——–+——-+

| Eid | Ename | City | Designation | Salary | Perks |

+—–+———+———-+——————-+——–+——-+

| 1 | Rahul | Delhi | Manager | 10300 | 853 |

| 2 | Gaurav | Mumbai | Assistant Manager | 10300 | 853 |

| 3 | Chandan | Banglore | Team Leader | 15450 | 999 |

| 5 | Tapan | Pune | Developer | 20600 | 1111 |

| 6 | Amar | Chennai | Developer | 16000 | 1124 |

| 7 | Santosh | Delhi | Designer | 10000 | 865 |

| 8 | Suman | Pune | Web Designer | 20000 | 658 |

+—–+———+———-+——————-+——–+——-+

7 rows in set (0.00 sec)

mysql> delimiter //

mysql> CREATE TRIGGER ins_trig BEFORE INSERT ON Emp

-> FOR EACH ROW

-> BEGIN

-> UPDATE Employee SET Salary=Salary-300 WHERE Perks>500;

-> END;

-> //

Query OK, 0 rows affected (0.01 sec)

mysql> delimiter ;

mysql> INSERT INTO Emp VALUES(9,’Rajesh’,’Delhi’,’Developer’,15000,658);

Query OK, 1 row affected (0.05 sec)

mysql> SELECT * FROM Employee;

+—–+———+———-+——————-+——–+——-+

| Eid | Ename | City | Designation | Salary | Perks |

+—–+———+———-+——————-+——–+——-+

| 1 | Rahul | Delhi | Manager | 10000 | 853 |

| 2 | Gaurav | Mumbai | Assistant Manager | 10000 | 853 |

| 3 | Chandan | Banglore | Team Leader | 15150 | 999 |

| 5 | Tapan | Pune | Developer | 20300 | 1111 |

| 6 | Amar | Chennai | Developer | 15700 | 1124 |

| 7 | Santosh | Delhi | Designer | 9700 | 865 |

| 8 | Suman | Pune | Web Designer | 19700 | 658 |

+—–+———+———-+——————-+——–+——-+

7 rows in set (0.00 sec)