$query1="UPDATE admin SET t_points=t_points+ (SELECT points from sites where url='$url') whereusername='$login_session'";如果子查询SELECT points from sites where url='$url'返回一些东西,那么查询就可以正常工作。如果不返回任何内容,则t
mysql_query("UPDATE users SET friends = CONCAT(friends,"$friend_id") WHERE username = '$user_logged_in'") or die mysql_error());mysql_query("UPDATE users SET friends = friends +" . ", " .