example for mysql client http://forum.nodejs.ru/index.php/topic,623.msg4049.html

controller.js

var Controller = function(req, res) {
    var DB = require("./db").DB;

    this._db = new DB();
    this._req = req;
    this._res = res;
    console.log(new Date() + ' : ' + req.url);
};

Controller.HTTP_OK_CODE = 200;
Controller.HEADERS = {
    'Content-Type': "text/plain",
    'charset':"utf-8"
};

Controller.prototype.sendCategories = function() {
    this._db.connect(function(){
	this._db.setDBForUTF8(function(){
	    this._selectCategories(this._send.bind(this));
	}.bind(this);
    }.bind(this));
};

Controller.prototype._send = function(err, results, fields) {
    if (err) {
	//throw err;
	res.end();
	client.end();
	return;
    }

    res.writeHead(Controller.HTTP_OK_CODE, Controller.HEADERS);

    res.end(JSON.stringify(results));
    client.end();
    delete this._db;
};

Controller.prototype._selectCategories = function(cb) {
    var url = require("url"),
    res = this._res,
    parentId = url.parse(this._req.url).pathname.split('/')[2];

    parentId = parentId == undefined?0:Number(parentId);

    var q = 'SELECT cat_id, cat_name FROM 4im_categories WHERE cat_parent_id = '+parentId;

    this._db.client.query(q,cb);
};

exports.Controller = Controller;

db.js

var Db = function() {
    var Client = require('mysql').Client;
    this.client = new Client();
}

Db.PASSWORD = "YYYYYY";
Db.USER = "XXXXX";
Db.DB = "my_db";

Db.prototype.connect = function(cb) {
    var client = this.client;
    client.user = Db.USER;
    client.password = Db.PASSWORD;
    
    this.afterConnect = cb;
    
    client.connect(this.setDB.bind(this));
};

Db.prototype.setDb = function(error, result){
    if(error) {
	console.log(error);
	return;
    }
    this.client.query("USE "+ Db.DB, function( error, result) {
	if(error){
	    console.log(error);
	    return;
	}
	this.afterConnect();
    }.bind(this));
};

Db.prototype.setDBForUTF8 = function(cb) {
    this.client.query("SET NAMES utf8", function(error, result){
	if(error) {
	    console.log(error);
	    return;
	}
	cb();
    });
};

exports.DB = Db;

index.js

var http = require('http');
var url = require("url");

http.createServer(

    function (req, res){
        var modname = url.parse(req.url).pathname.split('/')[1];

        try{
	    var mod = require("./"+modname);
	    var controller = new mod.Controller(req, res);
	    controller.sendCategories();
        }catch(e)
        {
            console.log(new Date() + ' : ' + e);
        }
    }

).listen(1337, "127.0.0.1");
console.log('Server running at http://127.0.0.1:1337/');