$select->joinInner(
     array('product_tierprice' => 'catalog_product_entity_tier_price'),
     'product_tierprice.entity_id=rp.product_id',
     array()
 );

$select->joinLeft(
    array('product_tierprice' => 'catalog_product_entity_tier_price'),
    'product_tierprice.entity_id=rp.product_id',
     array()
)->where('rp.product_id is NULL');