mysql 중복되는 rows 질문입니다....

얼마전에 jabber log 파싱해서 db 에넣기는 했습니다...그런데, cron 으로 매 10분마다 파싱하게 되어있는데...같은 data 가 계속 중복이 됩니다...물론 새로은 data도 입력되구요....

문제는 다음과 같습니다...

+-----+--------+-----------+------+-------+------+---------+------+-------------------------------------------------------+
| id | sender | recipient | year | month | date | time | am | message |
+-----+--------+-----------+------+-------+------+---------+------+-------------------------------------------------------+
| 653 | dlim | cdavis | 2006 | 2 | 07 | 4:00:42 | PM | i am going to be leaving in a minutes. see you later. |
| 654 | dlim | cdavis | 2006 | 2 | 07 | 4:00:42 | PM | i am going to be leaving in a minutes. see you later. |
+-----+--------+-----------+------+-------+------+---------+------+-------------------------------------------------------+

그 다음에는

+------+--------+-----------+------+-------+------+---------+------+-------------------------------------------------------+
| id | sender | recipient | year | month | date | time | am | message |
+------+--------+-----------+------+-------+------+---------+------+-------------------------------------------------------+
| 653 | dlim | cdavis | 2006 | 2 | 07 | 4:00:42 | PM | i am going to be leaving in a minutes. see you later. |
| 654 | dlim | cdavis | 2006 | 2 | 07 | 4:00:42 | PM | i am going to be leaving in a minutes. see you later. |
| 1315 | dlim | cdavis | 2006 | 2 | 07 | 4:00:42 | PM | i am going to be leaving in a minutes. see you later. |
| 1316 | dlim | cdavis | 2006 | 2 | 07 | 4:00:42 | PM | i am going to be leaving in a minutes. see you later. |
+------+--------+-----------+------+-------+------+---------+------+-------------------------------------------------------+

이런식 입니다....table 은 다음과 같습니다..
mysql> desc xml_log;
+-----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+----------------+
| id | int(11) | | PRI | NULL | auto_increment |
| sender | varchar(60) | | | | |
| recipient | varchar(60) | | | | |
| year | varchar(4) | | | | |
| month | char(3) | | | | |
| date | char(3) | | | | |
| time | varchar(10) | | | | |
| am | char(3) | YES | | NULL | |
| message | text | | | | |
+-----------+-------------+------+-----+---------+----------------+

어떤식으로 query를 해야 중복되는것을 막을수 있을까요? table 이 잘못 되었을까요?