Use Firebird Database to Lookup Data
The error is in the following line:

$query = db_select('EMPLOYEES', 't1',array('target' =&gt; 'import_employee')); 


It is selecting import_employee as target, and default as key, but in your settings.php file you have a default target with a import_employee key. Failing to find the definition for the target you select, Drupal fallbacks to using default as target and (without being instructed differently), to use default also as key. 

You can do one of the following:


Edit your settings.php file so that it contains information about the import_employee target and its default key. Keep in mind that the information about the database is given as $database['&lt;target&gt;']['&lt;key&gt;'], not $database['&lt;key&gt;']['&lt;target&gt;'].
Change your code to always call db_set_active() before your query.