title: Drupal 7 - module.install file schema error
body: <p>I have written below code in custom_notifications.install file.</p>
  
  <p>When I am trying to enable that module its giving me error "The website encountered an unexpected error. Please try again later."</p>
  
  <p>kindly help me with this.</p>
  
  <pre><code>function custom_notifications_schema() {
  
   $schema['custom_notification_log'] = array(
  'fields' =&gt; array(
    'cnl' =&gt; array('type' =&gt; 'serial', 'unsigned' =&gt; TRUE, 'not null' =&gt; TRUE),
    'notification_type' =&gt; array('type' =&gt; 'varchar', 'length' =&gt; 64),
    'notification_type_id' =&gt; array('type' =&gt; 'int', 'unsigned' =&gt; TRUE),
    'uid' =&gt; array('type' =&gt; 'int', 'unsigned' =&gt; TRUE),
    'viewed_on' =&gt; array('type' =&gt; 'int', 'unsigned' =&gt; TRUE),
  )
  );
  return $schema; 
  }
  </code></pre>