เกี่ยวกับ SQL ถามว่า Where 1 หมายถึงอะไร /และ คำสั่ง $where, $lnks ใช้สำหรับทำอะไร

$sq1 = mysql_query("SELECT * FROM tbl_place WHERE 1 $where AND status>0 ORDER BY id ASC" ); 
$r = mysql_fetch_assoc($sq1);

<?php
$kw = empty($_REQUEST['keyword']) ? "" : $_REQUEST['keyword'] ;
$pv = empty($_REQUEST['pprovince']) ? "" : $_REQUEST['pprovince'] ;
$ap = empty($_REQUEST['pampher']) ? "" : $_REQUEST['pampher'] ;
$tb = empty($_REQUEST['ptambol']) ? "" : $_REQUEST['ptambol'] ;
$cat = empty($_REQUEST['category']) ? "" : $_REQUEST['category'] ;
$pid = empty($_REQUEST['placecat']) ? "" : $_REQUEST['placecat'] ; #placetype

 $where = "";
 $lnks = "";

if($kw)	{ 	$where  .= " AND pname LIKE  '%$kw%' "; $lnks .="&keyword=".$kw.""; }
if($pv)	{ 	$where  .= " AND PROVINCE_ID='".$pv."' ";  $lnks .="&province=".$pv.""; }
if($ap)	{ 	$where  .= " AND AMPHUR_ID='".$ap."' ";   $lnks .="&ampher=".$ap.""; }
if($tb)	{ 	$where  .= " AND DISTRICT_ID='".$tb."'";   $lnks .="&tambol=".$tb.""; }
if($cat)	{ 	$where  .= " AND category='".$cat."' ";  $lnks .="&category=".$cat.""; }
if($pid)	{ 	$where  .= " AND placetype ='".$pid."' ";  $lnks .="&placecat=".$pid.""; } 


?>