title: MySQL update query, how to skip empty values?
body: <p>I've got such query:</p>
  
  <pre><code>$sql = "UPDATE test_accs SET 
      acc_owner = '$owner_id', 
      acc_policy_version = '$version', 
      acc_policy_last_update = '$approved', 
      acc_policy_next_update = '$renewed' 
          WHERE acc_id = '1'";
  </code></pre>
  
  <p>Now, all of these values on the web folmular are optional, one can set one of these values, two, or so. Now, after I submit the form, it goes in the query like that:</p>
  
  <pre><code>UPDATE test_accs SET acc_owner = '2', acc_policy_version = '1.2', acc_policy_last_update = '2012-12-19', acc_policy_next_update = '2012-12-18' WHERE acc_id = '1'
  </code></pre>
  
  <p>It works only when I submit all values from the form. Can you please show me how could it work even if not all the values has been sent, just for example one of them?</p>
  
  <p>When I set one value (f.ex. policy version), it looks like that:</p>
  
  <pre><code>UPDATE test_accs SET acc_owner = '', acc_policy_version = '1.2', acc_policy_last_update = '', acc_policy_next_update = '' WHERE acc_id = '1'
  </code></pre>
  
  <p>and it isn't working.</p>
  
  <p>It might be possible cause of the acc_owner table values?</p>
  
  <pre><code>#1366 - Incorrect integer value: '' for column 'acc_owner' at row 1
  </code></pre>
  
  <p>Thanks in advice.</p>
  
  <p>Form:</p>
  
  <pre><code>echo '&lt;td&gt;Change owner: &lt;select name="owner_id" onchange="showUser(this.value)" style="font-size:9px"&gt;&lt;option value=""&gt;Select a person:&lt;/option&gt;';
      while($owners = mysql_fetch_array($owners_query)) { echo '&lt;option value="'.$owners['id'].'"&gt;'.$owners['surname'].' '.$owners['name'].'&lt;/option&gt;&lt;/h2&gt;'; } echo '&lt;/select&gt;&lt;/td&gt;';
      echo "&lt;td&gt;&lt;input name='version' style='width:50px;text-align:center' placeholder='0.0' /&gt;&lt;/td&gt;";
      echo "&lt;td&gt;&lt;input name='approved' class='datepicker_all' readonly='readonly' style='text-align:center' placeholder='1999-01-01' /&gt;&lt;/td&gt;";
      echo "&lt;td&gt;&lt;input name='renewed' class='datepicker_all' readonly='readonly' style='text-align:center' placeholder='1999-01-01' /&gt;&lt;/td&gt;";
  </code></pre>