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mysql>
mysql>
mysql> delimiter $$
mysql>
mysql> CREATE TRIGGER myTrigger
->   BEFORE INSERT ON employee
->   FOR EACH ROW
-> BEGIN
->   DECLARE row_count INTEGER;
->
-> SELECT COUNT(*)
->     INTO row_count
-> FROM employee
-> WHERE id=NEW.id;
->
->   IF row_count > 0 THEN
-> UPDATE employee
->        SET salary = salary+NEW.salary
-> WHERE id=NEW.id;
->   ELSE
-> INSERT INTO employee (id,salary) VALUES(NEW.id,NEW.salary);
-> END IF;
->
-> END$$
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> delimiter ;
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->              values (1,'Jason',    'Martin',  '19960725',  '20060725', 1234.56, 'Toronto',  'Programmer');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(2,'Alison',   'Mathews',  '19760321', '19860221', 6661.78, 'Vancouver','Tester');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(3,'James',    'Smith',    '19781212', '19900315', 6544.78, 'Vancouver','Tester');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(4,'Celia',    'Rice',     '19821024', '19990421', 2344.78, 'Vancouver','Manager');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(5,'Robert',   'Black',    '19840115', '19980808', 2334.78, 'Vancouver','Tester');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(6,'Linda',    'Green',    '19870730', '19960104', 4322.78,'New York',  'Tester');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(7,'David',    'Larry',    '19901231', '19980212', 7897.78,'New York',  'Manager');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date,   salary,  City,       Description)
->               values(8,'James',    'Cat',     '19960917',  '20020415', 1232.78,'Vancouver', 'Tester');
ERROR 1442 (HY000): Can't update table 'employee' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
mysql>
mysql> select * from Employee;
Empty set (0.00 sec)

mysql>
mysql>
mysql>
mysql>
mysql> drop trigger myTrigger;
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql>
mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)