node + mysql 报错 error : Cannot enqueue Quit after invoking quit

var db_options={ host:'localhost', port : 3308, user : 'root', password : '', database:'mysql' } var mq = require("mysql"); var mc = mq.createConnection(db_options); mc.connect();

exports.getName = function(req, res) { var username = req.body["name"];

var sql = "select name from `user` where name = " + username;

mc.query(sql, function(err, rs, fields){
		mc.end(); 
		mc.destroy()
		var info="123";
		if(err){
			info = "系统异常";
			mc.end(); 
			mc.destroy()
			
		} 
		console.log(info);
		console.log(rs);
		res.write(JSON.stringify(rs));
		//console.log(JSON.stringify(rs));
		
});

};

我只是想写 用户名重复验证 $.ajax() 为什么会出现这样的问题！