I have something like this:
$sql = new Sql($this->tableGateway->getAdapter());
$select = $sql->select();
$select
-> from('mytable')
-> join('exp', 'field1_id=field1.id', '*', 'LEFT');
$where = new Where();
$where -> equalTo('field2_id', $field2_id);
$select->where($where);
$statement = $sql->prepareStatementForSqlObject($select);
but what if I want use "not equalTo"? How to do it?
You need to use notEqualTo
$where->notEqualTo('field2_id', $field2_id);
http://framework.zend.com/apidoc/2.1/classes/Zend.Db.Sql.Predicate.Predicate.html#notEqualTo