code: public function build()
      {
          if (!$this->isEmpty()) {
              return new SimpleQuery(
                  sprintf('SELECT id FROM %s WHERE %s', $this->tableName, $this->getProcedure()),
                  $this->getParameters(),
                  'id',
                  $this->connection
              );
          }
  
          return null;
      }
docs: Retrieve the filter rule if anything to filter.
  
  @return SimpleQuery|null