SQL/MySQL/Trigger/NEW

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Change NEW value in a before insert trigger

 
mysql>
mysql>
mysql> CREATE TABLE Employee(
    ->     id            int,
    ->     first_name    VARCHAR(15),
    ->     last_name     VARCHAR(15),
    ->     start_date    DATE,
    ->     end_date      DATE,
    ->     salary        FLOAT(8,2),
    ->     city          VARCHAR(10),
    ->     description   VARCHAR(15)
    -> );
Query OK, 0 rows affected (0.02 sec)
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)
mysql>
mysql>



Checking NEW value and create message

  
mysql>
mysql>
mysql> CREATE TABLE Employee(
    ->     id            int,
    ->     first_name    VARCHAR(15),
    ->     last_name     VARCHAR(15),
    ->     start_date    DATE,
    ->     end_date      DATE,
    ->     salary        FLOAT(8,2),
    ->     city          VARCHAR(10),
    ->     description   VARCHAR(15)
    -> );
Query OK, 0 rows affected (0.08 sec)
mysql>
mysql>
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.01 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql> CREATE TRIGGER myTrigger
    ->   BEFORE UPDATE
    ->       ON employee
    ->      FOR EACH ROW
    -> BEGIN
    ->    DECLARE dummy INT;
    ->    IF NEW.salary<0 THEN
    ->       SELECT `Account balance cannot be less than 0` INTO dummy
    ->         FROM employee
    ->        WHERE id=NEW.id;
    ->   END IF;
    -> END$$
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> drop trigger myTrigger;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql>
mysql>
mysql> update employee set salary = -1;
Query OK, 8 rows affected (0.01 sec)
Rows matched: 8  Changed: 8  Warnings: 0
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql>



Reference new value with NEW in a "BEFORE UPDATE"

 
mysql>
mysql>
mysql>
mysql> CREATE TABLE Employee(
    ->     id            int,
    ->     first_name    VARCHAR(15),
    ->     last_name     VARCHAR(15),
    ->     start_date    DATE,
    ->     end_date      DATE,
    ->     salary        FLOAT(8,2),
    ->     city          VARCHAR(10),
    ->     description   VARCHAR(15)
    -> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql>
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql> CREATE TRIGGER myTrigger
    -> BEFORE UPDATE ON employee
    -> FOR EACH ROW
    -> BEGIN
    ->     IF NEW.salary <5000 THEN
    ->       SET NEW.first_name=CONCAT("NEW.first_name","*");
    ->     ELSE
    ->       SET NEW.last_name=CONCAT("NEW.last_name","*");
    ->     END IF;
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql>
mysql> update employee set salary = 1000, first_name="new first Name";
Query OK, 8 rows affected (0.01 sec)
Rows matched: 8  Changed: 8  Warnings: 0
mysql>
mysql> select * from employee;
+------+-----------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name      | last_name | start_date | end_date   | salary  | city      | description |
+------+-----------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | NEW.first_name* | Martin    | 1996-07-25 | 2006-07-25 | 1000.00 | Toronto   | Programmer  |
|    2 | NEW.first_name* | Mathews   | 1976-03-21 | 1986-02-21 | 1000.00 | Vancouver | Tester      |
|    3 | NEW.first_name* | Smith     | 1978-12-12 | 1990-03-15 | 1000.00 | Vancouver | Tester      |
|    4 | NEW.first_name* | Rice      | 1982-10-24 | 1999-04-21 | 1000.00 | Vancouver | Manager     |
|    5 | NEW.first_name* | Black     | 1984-01-15 | 1998-08-08 | 1000.00 | Vancouver | Tester      |
|    6 | NEW.first_name* | Green     | 1987-07-30 | 1996-01-04 | 1000.00 | New York  | Tester      |
|    7 | NEW.first_name* | Larry     | 1990-12-31 | 1998-02-12 | 1000.00 | New York  | Manager     |
|    8 | NEW.first_name* | Cat       | 1996-09-17 | 2002-04-15 | 1000.00 | Vancouver | Tester      |
+------+-----------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql> update employee set salary = 6000, last_name="new last Name";
Query OK, 8 rows affected (0.00 sec)
Rows matched: 8  Changed: 8  Warnings: 0
mysql>
mysql> select * from employee;
+------+-----------------+----------------+------------+------------+---------+-----------+-------------+
| id   | first_name      | last_name      | start_date | end_date   | salary  | city      | description |
+------+-----------------+----------------+------------+------------+---------+-----------+-------------+
|    1 | NEW.first_name* | NEW.last_name* | 1996-07-25 | 2006-07-25 | 6000.00 | Toronto   | Programmer  |
|    2 | NEW.first_name* | NEW.last_name* | 1976-03-21 | 1986-02-21 | 6000.00 | Vancouver | Tester      |
|    3 | NEW.first_name* | NEW.last_name* | 1978-12-12 | 1990-03-15 | 6000.00 | Vancouver | Tester      |
|    4 | NEW.first_name* | NEW.last_name* | 1982-10-24 | 1999-04-21 | 6000.00 | Vancouver | Manager     |
|    5 | NEW.first_name* | NEW.last_name* | 1984-01-15 | 1998-08-08 | 6000.00 | Vancouver | Tester      |
|    6 | NEW.first_name* | NEW.last_name* | 1987-07-30 | 1996-01-04 | 6000.00 | New York  | Tester      |
|    7 | NEW.first_name* | NEW.last_name* | 1990-12-31 | 1998-02-12 | 6000.00 | New York  | Manager     |
|    8 | NEW.first_name* | NEW.last_name* | 1996-09-17 | 2002-04-15 | 6000.00 | Vancouver | Tester      |
+------+-----------------+----------------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql> drop trigger myTrigger;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>



Set NEW value to NULL in a before update trigger

 
mysql>
mysql>
mysql> CREATE TABLE Employee(
    ->     id            int,
    ->     first_name    VARCHAR(15),
    ->     last_name     VARCHAR(15),
    ->     start_date    DATE,
    ->     end_date      DATE,
    ->     salary        FLOAT(8,2),
    ->     city          VARCHAR(10),
    ->     description   VARCHAR(15)
    -> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql>
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");
Query OK, 1 row affected (0.02 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.02 sec)
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");
Query OK, 1 row affected (0.00 sec)
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");
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql>
mysql> CREATE TRIGGER myTrigger
    ->  BEFORE UPDATE ON employee FOR EACH ROW
    -> BEGIN
    ->   DECLARE dummy INT;
    ->
    ->   IF NEW.salary<0 THEN
    ->      SET NEW.salary=NULL;
    ->   END IF;
    ->
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> update employee set salary = -1;
Query OK, 8 rows affected (0.00 sec)
Rows matched: 8  Changed: 8  Warnings: 0
mysql>
mysql> drop trigger myTrigger;
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+--------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary | city      | description |
+------+------------+-----------+------------+------------+--------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 |   NULL | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 |   NULL | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 |   NULL | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 |   NULL | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 |   NULL | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 |   NULL | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 |   NULL | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 |   NULL | Vancouver | Tester      |
+------+------------+-----------+------------+------------+--------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql>
Источник — «http://sqle.ru/index.php?title=SQL/MySQL/Trigger/NEW&oldid=5258»