Views query alter

query_alter_example.php

function mymodule_views_query_alter(&$view, &$query) {
  if ($view->name == 'myview' ) {
    //Filter taxonomy by language
    global $language;
    $query->where[] = array(
      'conditions' => array(array(
        'field' => 'taxonomy_term_data.language',
        'value' => array($language->language),
        'operator' => 'in',
      )),
      'args' => array(),
      'type' => 'AND',
    );
  }elseif($view->name =='other_view' && $view->current_display == 'page'){
   //Add another table to the relation
   $query->add_table('field_data_field_evento_ciclo_agenda');
    
   //Get conditions and alter them	 
   $condiciones = $query->where['1']['conditions'];
   $query->where['1']['conditions'][] =  array(
			'field' => 'node.type',
			'value' => array('event'),
			'operator' => 'in',
		  );
   $query->where['1']['conditions'][] =   array(
			'field' => 'field_data_field_evento_ciclo_agenda.field_evento_ciclo_agenda_nid',
			'value' => array(),
			'operator' => 'IS NULL',
		  );
   //Add an extra condition
   $condiciones[] =  array(
			'field' => 'node.type',
			'value' => array('season'),
			'operator' => 'in',
		  );
	 
   //Update conditions in query
   $query->where[] = array(
      'conditions' => $condiciones,
      'args' => array(),
      'type' => 'AND',
    );
	
 }
}