INSERT ON DUPLICATE KEY UPDATE

feel this useful,copy from here
http://stackoverflow.com/questions/548541/insert-ignore-vs-insert-on-duplicate-key-update


CREATE TABLE `users_partners` (
`uid` int(11) NOT NULL DEFAULT '0',
`pid` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`uid`,`pid`),
KEY `partner_user` (`pid`,`uid`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8

INSERT INTO users_partners (uid,pid) VALUES (1,1);
...1 row(s) affected

INSERT INTO users_partners (uid,pid) VALUES (1,1);
...Error Code : 1062
...Duplicate entry '1-1' for key 'PRIMARY'

INSERT IGNORE INTO users_partners (uid,pid) VALUES (1,1);
...0 row(s) affected

INSERT INTO users_partners (uid,pid) VALUES (1,1) ON DUPLICATE KEY UPDATE uid=uid
...0 row(s) affected

REPLACE INTO users_partners (uid,pid) VALUES (1,1)
...2 row(s) affected

INSERT INTO users_partners (uid,pid) VALUES (1,1),(1,2),(1,3),(1,4)
...Error Code : 1062
...Duplicate entry '1-1' for key 'PRIMARY'

INSERT IGNORE INTO users_partners (uid,pid) VALUES (1,1),(1,2),(1,3),(1,4)
...3 row(s) affected

INSERT INTO users_partners (uid,pid) VALUES (1,1),(1,2),(1,3),(1,4) ON DUPLICATE KEY UPDATE uid=uid
...3 row(s) affected

REPLACE INTO users_partners (uid,pid) VALUES (1,1),(1,2),(1,3),(1,4)
...5 row(s) affected