magento using join in grid.php prepareCollection

Answer 1

Try this:

$collection->getSelect()
          ->join($this->getTable('faqcat/faqcat'), "faqcat.faqcat_id = main_table.faqcat_id", array(faqcat.*));

You can see the sql that will actually be run to fetch the collection by:

Mage::log($collection->getSelect()->__toString());

The Varien_Db_Select class is based on Zend_Db_Select, so the Zend documentation is a good reference.