mysql - Selecting column alias filled with NULLs with Zend_Db -

is there way can select null column zend_db. make clear, write query:

select id, name, age, null ssn dummy_table;  

the result have 4 columns id, name, age , ssn(filled null). there way in zend_db. guess was:

$columns = [     'id' => 'id',     'name' => 'name',     'age' => 'age',     null => 'ssn' ]; $select = $this->_db->select(); $select     ->from('dummy_table', $columns) 

but won't work generate:

select `dummy_table`.`id` `id`, `dummy_table`.`name` `name`, `dummy_table`.`age` `age`, `dummy_table`.`ssn` `` `dummy_table`; 

this query fail. there way using zend_db ($this->_db->query('') not option)?

have tried using new zend_db_expr('null') ?

you :

$null = new zend_db_expr('null');  $columns = [     'id' => 'id',     'name' => 'name',     'age' => 'age',     $null => 'ssn' ]; $select = $this->_db->select(); $select     ->from('dummy_table', $columns);