如何获取更新后生成的哈希？
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)
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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:~$
另外，在工作台上，我看到了旧触发器：
但看不到如何添加额外的触发器。