insert new record and update if already exist
lets say you want to do this rule
1. Insert record if record is new record
2. update record if record already exist.
To do that, you can use INSERT … ON DUPLICATE KEY UPDATE syntax for example
INSERT INTO table(a,b,c) VALUES (1,2,3)
ON DUPLICATE KEY UPDATE c=c+1;
more info http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
