MySQL Query Not Working PHP

I have a query I'm trying to build so that I can filter by car brand. But if a certain session variable exists, it'll ask for an extra part to be added to the query which is basically limiting the results to the logged in branch. Here's the query:

$query_AUCTION = "SELECT * 
          FROM at_auction AS a 
          JOIN at_brands AS b ON a.aCarBrandID = b.bid 
      ORDER BY b.brand $orderx";

... now this w开发者_开发技巧orks but where can I add a:

"WHERE bid = '{$bid}'"? ...or a... "AND bid = '{$bid}'";

It brings up an error.

insert your where clauses BEFORE your order by

$query_AUCTION = "SELECT * FROM at_auction AS a JOIN at_brands AS b ON a.aCarBrandID = b.bid WHERE bid = '{$bid}' ORDER BY b.brand $orderx";

Use a generic WHERE 1=1 and if you want to insert additional condition:

$query_AUCTION = "SELECT * 
          FROM at_auction AS a 
          JOIN at_brands AS b ON a.aCarBrandID = b.bid
          WHERE 1=1 ";

if ($bid > 0)
   $query_AUCTION .= " AND bid = '{$bid}' ";

$query_AUCTION .= " ORDER BY b.brand $orderx";

try this :

$query_AUCTION = "SELECT * 
                  FROM at_auction AS a 
                  JOIN at_brands  AS b ON ( b.bid = a.aCarBrandID ) ";

if( isset( $_SESSION['bid'] ) )
{
    $query_AUCTION.= " WHERE b.bid = '".$_SESSION['bid']."'";
}

$query_AUCTION.= " ORDER BY b.brand $orderx";