Help with multipule drop down lists in a select query

Question

Hi I am trying to design a search query using 5 drop down lists coming from tables.  the front end looks like this
I have the selections going to variables then by $_POST into the msqyl query my other code is
MY CODE FOR THE FORM IS
  <form action="horse-events-devon.php?url_countyid=<?php echo  urlencode ($url_countyid ['url_countyid'])  ; ?>&go" method="POST">
    <table id="searchtable">
      <tr>
        <th>Find By Discipline</th>
        <th>Find By Venue</th>
        <th>Find By Championship</th>
        <th>Find By Organiser</th>
        <th>Equine Association</th>
        <th>Submit Your Selections</th>
        </tr>
      <tr>
        <td><select name="dis_id">
                                    <?php
                                        $upcomingdis = upcomingdis($url_countyid);
                                        $upcoming_dis_bycounty = mysql_fetch_assoc ($upcomingdis);
                                    ?>
                                    <?php
                                    do {
                                      ?>   <option value="<?php echo $upcoming_dis_bycounty ['dis_id']; ?>" >
                                    <?php echo $upcoming_dis_bycounty ['dis_description']; ?></option>
                                    <?php
                                    } while ($upcoming_dis_bycounty = mysql_fetch_assoc ($upcomingdis));
                                    ?></select></td>
        <td><select name="ven_id">
                                    <?php
                                        $upvenbycounty_set = upcoming_venevents_bycounty($url_countyid);
                                        $upcoming_ven_bycounty = mysql_fetch_assoc ($upvenbycounty_set);
                                    ?>
                                    <?php
                                    do {
                                      ?>   <option value="<?php echo $upcoming_ven_bycounty ['ven_id']; ?>" >
                                    <?php echo $upcoming_ven_bycounty ['ven_name']; ?></option>
                                    <?php
                                    } while ($upcoming_ven_bycounty = mysql_fetch_assoc ($upvenbycounty_set));
                                    ?></select></td>
        <td><select name="champ_id">
                                    <?php
                                        $championship_set = findchampionships();
                                        $champlist = mysql_fetch_assoc ($championship_set);
                                    ?>
                                    <?php
                                    do {
                                    ?>   <option value="<?php echo $champlist ['champ_id']; ?>" >
                                    <?php echo $champlist ['champ_description']; ?></option>
                                    <?php
                                    } while ($champlist = mysql_fetch_assoc ($championship_set));
                                    ?></select></td>
        <td>
        <select name="org_id">
                        <?php
                            $uporgbycounty_set = upcoming_organevents_bycounty($url_countyid);
                            $upcoming_org_bycounty = mysql_fetch_assoc ($uporgbycounty_set);
                        ?>
                        <?php
                        do {
                        ?>   <option value="<?php echo $upcoming_org_bycounty ['org_id']; ?>" ><?php echo $upcoming_org_bycounty ['org_name']; ?></option>
                        <?php
                        } while ($upcoming_org_bycounty = mysql_fetch_assoc ($uporgbycounty_set));
                        ?></select>
        </td>
        <td><select name="***_id">
                                    <?php
                                        $upassbycounty_set = upcoming_assevents_bycounty($url_countyid);
                                        $upcoming_assbycounty = mysql_fetch_assoc ($upassbycounty_set);
                                    ?>
                                    <?php
                                    do {
                                    ?>   <option value="<?php echo $upcoming_assbycounty ['***_id']; ?>" >
                                    <?php echo $upcoming_assbycounty ['***_description']; ?></option>
                                    <?php
                                    } while ($upcoming_assbycounty = mysql_fetch_assoc ($upassbycounty_set));
                                    ?></select></td>
          <td><input name="submit" type="submit" /><input name="countyid" type="hidden" value="<?php echo $url_countyid ['url_countyid']; ?>" /></td>
        </tr>
      </table>
  </form>
  <?php
if (isset($_POST['submit'])){
    if (isset($_GET['go'])){
    $countyid = $_POST['countyid'];
    $ven_id = $_POST['ven_id'];
    $dis_id = $_POST['dis_id'];
    $champ_id = $_POST['champ_id'];
    $org_id = $_POST['org_id'];
    $event_id = $row['event_id'];
        $sql = "SELECT DATE_FORMAT (events.startdate, '%a, %d, %b')
                   AS stdate, events.event_id, events.title, events.ven_id, events.org_id,
                   venue.county_id, venue.ven_id, eventdisciplines.event_id, eventdisciplines.dis_id, county.county_id, discipline.dis_id \n"
            . "FROM events \n"
            . "LEFT OUTER JOIN eventdisciplines \n"
            . "ON events.event_id = eventdisciplines.event_id \n"
            . "LEFT OUTER JOIN discipline \n"
            . "ON eventdisciplines.dis_id = discipline.dis_id \n"
            . "LEFT OUTER JOIN venue \n"
            . "ON events.ven_id = venue.ven_id \n"
            . "LEFT OUTER JOIN county \n"
            . "ON venue.county_id = county.county_id \n"
            . "WHERE events.ven_id = ({$ven_id} OR events.org_id = {$org_id})\n"
            . "AND events.startdate > NOW()\n"
            . "AND venue.county_id = {$countyid}  \n"
            . "ORDER BY startdate ASC";
    $result = mysql_query ($sql, $connection);
?>
My problem is at the WHERE point,  how do I code for single and multipule selections,  The       . "WHERE events.ven_id = ({$ven_id} OR events.org_id = {$org_id})\n" throws and error.
How am I best programing this type of query,  ??  Should it be with php ??

Answer 1

The best thing is to dynamically build your where clause based on the user selection. Test the values of all form fields and if the user does not make a selection, do not include that in the where clause.
Trying to build a single, static where clause that accounts for all possible user input permutations is extremely difficult.