concatenate fields in select

Hello,

It´s posible to do something like this?

$out['cambio_divisas'] = $db
                ->query( 'select', 'cambio_divisas' )
                ->get( 'id_moneda as value, moneda + " " + id_moneda as label' )                 
                ->order('id_moneda ASC')
                ->exec()
                ->fetchAll();

I need to put as a label of select two concatenated fields (moneda + " " + id_moneda), but this not works.

Thank you!