code: protected function buildDefaultString()
      {
          if ($this->default === null) {
              return $this->isNotNull === false ? ' DEFAULT NULL' : '';
          }
  
          $string = ' DEFAULT ';
          switch (gettype($this->default)) {
              case 'integer':
                  $string .= (string) $this->default;
                  break;
              case 'double':
                  // ensure type cast always has . as decimal separator in all locales
                  $string .= StringHelper::floatToString($this->default);
                  break;
              case 'boolean':
                  $string .= $this->default ? 'TRUE' : 'FALSE';
                  break;
              case 'object':
                  $string .= (string) $this->default;
                  break;
              default:
                  $string .= "'{$this->default}'";
          }
  
          return $string;
      }
docs: Builds the default value specification for the column.
  @return string string with default value of column.