syntax for before update trigger to generate hash - mysql

Question

How do I get the hash generated after updates?
thufir#dur:~$
thufir#dur:~$ mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 138
Server version: 5.1.58-1ubuntu1 (Ubuntu)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> use nntp;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+---------------------+
| Tables_in_nntp |
+---------------------+
| articles |
| newsgroups |
| newsgroups_articles |
+---------------------+
3 rows in set (0.00 sec)
mysql> describe newsgroups;
+-----------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+----------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| newsgroup | longtext | NO | | NULL | |
| hash | char(32) | NO | | NULL | |
+-----------+----------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> show triggers;
+-----------+--------+------------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| Trigger | Event | Table | Statement | Timing | Created | sql_mode | Definer | character_set_client | collation_connection | Database Collation |
+-----------+--------+------------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| make_hash | INSERT | newsgroups | BEGIN
set new.hash = md5(new.newsgroup);
END | BEFORE | NULL | | root#localhost | utf8 | utf8_general_ci | latin1_swedish_ci |
+-----------+--------+------------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> DELIMITER $$
mysql>
mysql> USE `nntp`$$
Database changed
mysql> CREATE
-> TRIGGER `nntp`.`make_hash_update`
-> AFTER UPDATE ON `nntp`.`newsgroups`
-> FOR EACH ROW
-> BEGIN
-> set old.hash = md5(new.newsgroup);
-> END$$
ERROR 1362 (HY000): Updating of OLD row is not allowed in trigger
mysql>
mysql> quit;
-> exit
-> ^CCtrl-C -- exit!
Aborted
thufir#dur:~$
Also, from the workbench, I see the old trigger:
but don't see how to add an additional trigger.

Answer 1

It's not after update, it's before update, and new. Don't quite understand the syntax, but this at least doesn't generate syntax errors. Would've like to have use the workbench:
thufir#dur:~$
thufir#dur:~$ mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 144
Server version: 5.1.58-1ubuntu1 (Ubuntu)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> use nntp;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show triggers;
+-----------+--------+------------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| Trigger | Event | Table | Statement | Timing | Created | sql_mode | Definer | character_set_client | collation_connection | Database Collation |
+-----------+--------+------------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
| make_hash | INSERT | newsgroups | BEGIN
set new.hash = md5(new.newsgroup);
END | BEFORE | NULL | | root#localhost | utf8 | utf8_general_ci | latin1_swedish_ci |
+-----------+--------+------------+-----------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+
1 row in set (0.00 sec)
mysql> show create trigger make_hash;
+-----------+----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
| Trigger | sql_mode | SQL Original Statement | character_set_client | collation_connection | Database Collation |
+-----------+----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
| make_hash | | CREATE DEFINER=`root`#`localhost` TRIGGER `nntp`.`make_hash`
BEFORE INSERT ON `nntp`.`newsgroups`
FOR EACH ROW
BEGIN
set new.hash = md5(new.newsgroup);
END | utf8 | utf8_general_ci | latin1_swedish_ci |
+-----------+----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
1 row in set (0.00 sec)
mysql>
mysql> DELIMITER $$
mysql>
mysql> USE `nntp`$$
Database changed
mysql> CREATE
-> TRIGGER `nntp`.`make_hash_update`
-> BEFORE UPDATE ON `nntp`.`newsgroups`
-> FOR EACH ROW
-> BEGIN
-> set new.hash = md5(new.newsgroup);
-> END$$
Query OK, 0 rows affected (0.19 sec)
mysql>
mysql> show triggers;
-> ^CCtrl-C -- exit!
Aborted
thufir#dur:~$