magento sql 常用用法

  $resource = Mage::getSingleton('core/resource');  
  $tableName_votes = $resource->getTableName('jselfless/votes');  
  $tableName_image = $resource->getTableName('jselfless/image');  
  $collection = Mage::getModel('jselfless/woman')->getCollection();  
  $collection->getSelect()->reset(Zend_Db_Select::COLUMNS);  
  $collection->getSelect()->columns(array('items_count'=>'count(main_table.id)'));  
  $collection->addFieldToFilter('main_table.year',date('Y'));  
  $collection->addFieldToFilter('image.type','main');  
  $collection->addFieldToFilter('award',array('eq'=>''));  
  $collection->getSelect()->join(array('votes' => $tableName_votes), 'main_table.id = votes.selfless_woman_id', '');  
  $collection->getSelect()->join(array('image' => $tableName_image), 'main_table.id = image.selfless_woman_id', array('image.*'));  
  $collection->getSelect()->group('main_table.id');  
  $collection->getSelect()->Order('items_count desc');  
  $collection->getSelect()->Order('votes.created_at desc');  
  $collection->getSelect()->Order('main_table.updated_at desc');  
  $collection->getSelect()->limit(10,$postData['offset']);