Magento collection filtering nested where condition simple notation

Use only $collection->addfieldtofilter (), do not use Addattributetofilter () or zend_db_expr (can be used for more complex where statements) such as: collection- >getselect ()->where (New zend_db_expr ("E.created_at > ' 2013-01-01 00:00:00 ' OR e.created_at < ' 2012-01-01 00:00:00)); and relationship------------------------------------------------------Min_weight < $weight andmax_weight >= $weight

$_collection Array $weight )) (array$weight));

OR relationship------------------------------------------------------min_weight > $weight or$weight > Max_weight

$_collection-addfieldtofilter (array(' min_weight ', ' max_weight '),    array  (        array$weight),        array$weight))    ;    

And and or nesting relationships------------------------------------------------------min_weight > $weight and ($weight <= max_ Weight and max_weight<>nullormax_weight is NULL)

$_collection Array $weight )-addfieldtofilter (    array(' max_weight ', ' max_weight '),    array (        array$weighttrue),        Array true )    ));            

Magento collection filtering nested where condition simple notation