On Wed, 2010-09-22 at 15:05 +0530, sivaji j.g wrote:

I assume this is with an intention of avoiding duplicate records inserts. However in my case db_affected_rows() mostly returns 0 though a matching row is found in the table.

I guess it is because the values being updated is same as values already available in the row.

Yes, as MySQL documentation clearly states:

For UPDATE statements, the affected-rows value by default is the number of rows actually changed. If you specify the CLIENT_FOUND_ROWS flag to mysql_real_connect() when connecting to mysqld, the affected-rows value is the number of rows “found”; that is, matched by the WHERE clause.

http://dev.mysql.com/doc/refman/5.1/en/mysql-affected-rows.html