/**
  * Removes the result of query from this query.
  *
  * @param DataQuery $subtractQuery
  * @param string $field
  * @return $this
  */
 public function subtract(DataQuery $subtractQuery, $field = 'ID')
 {
     $fieldExpression = $subtractQuery->expressionForField($field);
     $subSelect = $subtractQuery->getFinalisedQuery();
     $subSelect->setSelect(array());
     $subSelect->selectField($fieldExpression, $field);
     $subSelect->setOrderBy(null);
     $subSelectSQL = $subSelect->sql($subSelectParameters);
     $this->where(array($this->expressionForField($field) . " NOT IN ({$subSelectSQL})" => $subSelectParameters));
     return $this;
 }