protected function _buildFilter($value, $isSearchValue)
    {
        if ($isSearchValue) {
            //is search string, using LIKE
            $query = " like " . \OxidEsales\Eshop\Core\DatabaseProvider::getDb()->quote('%' . $value . '%') . " ";
        } else {
            //not search string, values must be equal
            $query = " = " . \OxidEsales\Eshop\Core\DatabaseProvider::getDb()->quote($value) . " ";
        }

        return $query;
    }