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Have a look at the method Mage_Core_Model_Resource_Db_Collection_Abstract::addExpressionFieldToSelect():

/**
 * Add attribute expression (SUM, COUNT, etc)
 * Example: ('sub_total', 'SUM({{attribute}})', 'revenue')
 * Example: ('sub_total', 'SUM({{revenue}})', 'revenue')
 * For some functions like SUM use groupByAttribute.
 *
 * @param string $alias
 * @param string $expression
 * @param array $fields
 * @return Mage_Core_Model_Resource_Db_Collection_Abstract
 */
public function addExpressionFieldToSelect($alias, $expression, $fields)
{
    // validate alias
    if (!is_array($fields)) {
        $fields = array($fields=>$fields);
    }

    $fullExpression = $expression;
    foreach ($fields as $fieldKey=>$fieldItem) {
        $fullExpression = str_replace('{{' . $fieldKey . '}}', $fieldItem, $fullExpression);
    }

    $this->getSelect()->columns(array($alias=>$fullExpression));

    return $this;
}

Usage

$collection->addExpressionFieldToSelect("page_view", "sum({{page_view}})", ["page_view"]);
//                                      ^ alias      ^ expression          ^ used fields

$collection->getSelect()->group("page_view");