code: public function scalar($attribute, $db = null)
      {
          if ($this->emulateExecution) {
              return null;
          }
  
          $record = $this->one($db);
          if ($record !== null) {
              return $record->hasAttribute($attribute) ? $record->$attribute : null;
          } else {
              return null;
          }
      }
docs: Returns the query result as a scalar value.
  The value returned will be the specified attribute in the first record of the query results.
  @param string $attribute name of the attribute to select
  @param Connection $db the database connection used to execute the query.
  If this parameter is not given, the `db` application component will be used.
  @return string the value of the specified attribute in the first record of the query result.
  Null is returned if the query result is empty.