remove last comma in string

From:	weetat	Date:	Fri, 09 Jun 2006 00:58:46 +0000
Subject:	remove last comma in string
Groups:	php.general
Request:	Send a blank email to php-general+get-237653@lists.php.net to get a copy of this message

Hi all, I am using php 4.3.2 and mysql , linux. I have a sql statement below :

    UPDATE tbl_chassis_temp SET  country = 'Singapore',  city 'SINGAPORE',  building = 'Tampines Central 6',  other = 'Level 03-40',

I need to remove the last comma from sql text above. I have tried using substr and rtrim , without any success ? Anyone have any suggestion ? THanks - weetat