public function select(array $fields)
    {
        if (empty($fields)) {
            throw new InvalidArgumentException('The field array must not be' .
                ' empty.');
        }

        foreach ($fields as $field) {
            $validationResult = QueryValidator::validateFieldName($field);
            if ($validationResult->isFailed()) {
                throw new InvalidArgumentException('The field array for' .
                    ' building the SELECT clause contains invalid field name.' .
                    ' Validation fail reason: ' .
                    $validationResult->getFailReason());
            }
        }

        // Flipping an array will create a new associative array. The keys of
        // the new associative array make a set of distinct fields.
        $distinctFields = array_flip($fields);
        $this->selectFields = array_keys($distinctFields);
    }