code: protected function buildCol()/*# : array */
      {
          $result = [];
  
          foreach ($this->col_defs as $col) {
              $res = [];
              // name
              $res[] = $this->quote($col['name']);
  
              // type
              $res[] = $col['type'];
  
              // not null ?
              if (isset($col['notNull'])) {
                  $res[] = 'NOT NULL' .
                      ($col['notNull'] ? (' '.$col['notNull']) : '');
              }
  
              // default ?
              if (isset($col['default'])) {
                  $res[] = 'DEFAULT ' . ($col['default'][1] ? $col['default'][0] :
                      $this->processValue($col['default'][0]));
              }
  
              // auto
              if (isset($col['autoincrement'])) {
                  $res[] = 'AUTO_INCREMENT';
              }
  
              // unique
              if (isset($col['unique'])) {
                  $res[] = 'UNIQUE' .
                      ($col['unique'] ? (' ' . $col['unique']) : '');
              }
  
              // primary
              if (isset($col['primary'])) {
                  $res[] = 'PRIMARY KEY' .
                      ($col['primary'] ? (' ' . $col['primary']) : '');
              }
  
              // other constraints
              if (isset($col['constraint'])) {
                  $res[] = join(' ', $col['constraint']);
              }
  
              array_walk($res, function($m) { return trim($m); });
              $result[] = join(' ', $res);
          }
          return $result;
      }
docs: Build column definitions
  
  @return array
  @access protected