Create Select query with join using Zend Framework

$this->db->select()->from(array('T1'=>'TBL_1'),array('table1_id'))
->join(array('T2'=>'TBL_2'),
'T1.site_id = T2.site_id',
array('GROUP_CONCAT( T2.name) as site_name'))
->where('T1.table1_id = ?',mysql_escape_string($tableId))

Set common view file in controller for using in different actions

We can use the same view file for different actions by using the view render helper.
If we want to use the same view file for Add and Edit pages, Create a view file for Add and use the below code in the Edit action function
$this->_helper->viewRenderer->setRender('add');