NodeJs项目Express + MySQL 提示:Can't set headers after they are sent.

错误提示：Can't set headers after they are sent.

错误意思：响应头文件未设置，数据已经发送

错误代码：

router.get('/', function(req, res, next) { 
	var movies; 
	db.DBConnection.query( 
	'select * from movie', 
	  function(err, result) { 
		console.log(result); 
		movies = result; 
	  } 
	); 
   res.render('index.jade',{ 
        title:'网站首页', 
        movies: movies 
    }); 
});

正确代码：

//访问网站跟目录：localhost:3000/ 
router.get('/', function(req, res, next) { 
	var movies; 
	db.DBConnection.query( 
	'select * from movie', 
	  function(err, result) { 
		return res.render('index.jade',{ 
			title:'网站首页', 
			movies: result 
		}); 
	  } 
	);  
});

总结：MySQL 数据查询，直接在回调函数中，数据相关数据和页面