protected function buildColumnsClause() {
		if (empty($this->columnList)) {
			if (!empty($this->value))				
				$this->columnList = array_keys($this->value);
			else
				return '';
		}
		
		$columns = [];
		
		foreach ($this->columnList as $column)
			$columns[] = $this->translateColumn($column);
			
		return implode(',', $columns);
	}