code: protected function buildFrom()/*# : array */
      {
          $result = [];
          foreach ($this->clause_table as $as => $tbl) {
              // table alias
              $alias = is_int($as) ? '' : (' AS ' . $this->quoteSpace($as));
  
              // subselect
              if (is_object($tbl) && $tbl instanceof SelectStatementInterface) {
                  $tbl = '(' . $tbl->getStatement([], false) . ')';
  
              // normal table
              } else {
                  $tbl = $this->quote($tbl);
              }
              $result[] = $tbl . $alias;
          }
          return $result;
      }
docs: Build FROM
  
  @return array
  @access protected