Mysql primary key when using INSERT INTO ... ON DUPLICATE KEY UPDATE - mysql

Question

My table structure is:
CREATE TABLE IF NOT EXISTS `users_settings_temp` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`userid` int(10) unsigned DEFAULT NULL,
`type` enum('type1','type2')
`data` text,
`date_created` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
What I am trying to do is:
Let say I want to insert a new entry, but I dont want it to be duplicate, after google around, i found this format:
INSERT INTO users_settings_temp(...)
ON DUPLICATE KEY UPDATE data = '{$data}'
I guess the problem is in my table, the primary key => id. How do I alter the table, so that I could use the:
INSERT INTO ... ON DUPLICATE KEY UPDATE
Can I use user_id + type as primary key? If yes, could you please show me how to do it?

Answer 1

CREATE TABLE IF NOT EXISTS `users_settings_temp` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`userid` int(10) unsigned DEFAULT NULL,
`type` enum('type1','type2'),
`data` text,
`date_created` int(11) DEFAULT NULL,
PRIMARY KEY (`id`, `type`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
When you do it like this then
a) specifying id works
mysql> INSERT INTO users_settings_temp VALUES (1, 2, 'type1', 'keks', 5);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO users_settings_temp VALUES (1, 2, 'type2', 'keks', 5);
Query OK, 1 row affected (0.00 sec)
b) of course primary key is guaranteed to be unique
mysql> INSERT INTO users_settings_temp VALUES (1, 2, 'type2', 'keks', 5);
ERROR 1062 (23000): Duplicate entry '1-type2' for key 'PRIMARY'
c) letting database pull a new id works
mysql> INSERT INTO users_settings_temp VALUES (NULL, 2, 'type2', 'keks', 5);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO users_settings_temp VALUES (NULL, 2, 'type1', 'keks', 5);
Query OK, 1 row affected (0.00 sec)
but will increase them always
mysql> SELECT * FROM users_settings_temp;
+----+--------+-------+------+--------------+
| id | userid | type | data | date_created |
+----+--------+-------+------+--------------+
| 1 | 2 | type1 | keks | 5 |
| 1 | 2 | type2 | keks | 5 |
| 2 | 2 | type2 | keks | 5 |
| 3 | 2 | type1 | keks | 5 |
+----+--------+-------+------+--------------+
4 rows in set (0.00 sec)
NOTES:
You should think if your id should still be autoincrement or not.
Also, can not think of a reason why date_created should be int(11) instead of datetime