How to join tables with hook_views_data
$data['activity_teamie']['table']['join'] = array(
  'activity_teamie_map' =&gt; array(
    'left_field' =&gt; 'aid',
    'field' =&gt; 'aid'
  )
);


You actually want to join the other way round.kk

A general tip, try to think of some kind of similar join relation in Drupal core and look it up in views/modules/$module.views.inc

$data['activity_teamie']['entity_id'] = array(


Isn't entity_id part of activity_teamie_map?