Drupal watchdog query into file

To avoid record growing in watchdog table I am doing the followings. outfile in mysql is used to write output in a file.
I am using following code to write watchdog output into file.

<?php
function customfunction() {
$datetime = date("Y_m_d_Hi");
$path = "c:/";
db_query("SELECT wid,type,uid,message,severity,link,location,referer,hostname,timestamp FROM watchdog ORDER BY wid DESC LIMIT 0,10 INTO OUTFILE '".$path."watchdog".$datetime.".csv' FIELDS TERMINATED BY ',' ENCLOSED BY '\"' LINES TERMINATED BY '\n' ");
}
?>