Compilation Error in MYSQL trigger? - mysql

Question

Table structure is:
mysql> DESC groups;
+--------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+--------------+------+-----+---------+-------+
| PKey | varchar(64) | NO | PRI | NULL | |
| group_name | varchar(64) | YES | | NULL | |
| Region | varchar(128) | NO | | NULL | |
| Role | varchar(128) | NO | | NULL | |
| parent_group | varchar(64) | NO | MUL | NULL | |
+--------------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
When i am executing this Trigger , i'm having a compilation error
DELIMITER $$
CREATE
TRIGGER `group_before_delete` BEFORE DELETE
ON `groups`
FOR EACH ROW BEGIN
IF old.parent_group=old.PKey THEN
UPDATE `Error: deletion RootGroup is prohibited!`;
ELSE
UPDATE groups
SET parent_group=old.parent_group
WHERE parent_group=old.Pkey;
END IF;
END$$
DELIMITER ;
ERROR 1064 (42000): You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version for the
right syntax to use near ';
ELSE
t_group=old.parent_group
t_group=old.PKey;
END IF;' at line 6
mysql> DELIMITER ;
Can you tell me what i'm missing here ??

Answer 1

You get an error in your code because the syntax of your UPDATE statement is not valid.
The links you give are 4 and 5 years old!
Since the SIGNAL statement is available in MySQL since version 5.5.0 (released 3 years ago), this is really not a good idea to use the hacks described in these 2 webpages. Instead, use the SIGNAL statement.
Note: From the comments we learn that the OP is not using MySQL 5.5, so SIGNAL is not available.

Answer 2

In your IF statement, the following is not a valid SQL statement:
UPDATE `Error: deletion RootGroup is prohibited!`;
This should be this:
IF old.parent_group=old.PKey THEN
UPDATE `Error: deletion RootGroup is prohibited!` set x=1;
ELSE
UPDATE groups
SET parent_group=old.parent_group
WHERE parent_group=old.PKey;
END IF;
I have never done things this way. It is a bit of an ugly way of doing it. But if it works, what the heck.