gistfile1.js

/**
 * Example reading multiple databaserequests simultaniously
 * while calling the callback-Fn only when all request have finished
 *
 * In this example, we want to read a table with all area's in a specific country.
 * From there on, from every area we need to know the citienames and population, which resides in a second table.
 * 
 * In some situations, this might be done with one statement using INNER JOIN, but there are cases where you need multiple requests. (performance or limitation)
 *
 * The array is build, has this form:
 * 
 * [
 *     {
 *         'areaid' : 1,
 *         'name' : 'Gelderland',
 *         'cities' : [
 *             {
 *                 'id' : 42,
 *                 'cityname' : Arnhem,
 *                 'population' : 70.000
 *             },
 *             {
 *                 'id' : 26,
 *                 'cityname' : Nijmegen,
 *                 'population' : 80.000
 *             }
 *     },
 *     {
 *         'areaid' : 2,
 *         'name' : 'Overijssel',
 *         'cities' : [
 *             {
 *                 'id' : 21,
 *                 'cityname' : Enschede,
 *                 'population' : 90.000
 *             },
 *             {
 *                 'id' : 18,
 *                 'cityname' : Hengelo,
 *                 'population' : 40.000
 *             }
 *     }
 * ]
 * 
*/


YUI.add('MyModelFoo', function(Y, NAME) {

    var mysqlClient =require('mysql');
    var mysqlConfig = {
        host : 'localhost',
        port : 3306,
        user : 'myusername',
        password : 'mypassword',
        database : 'mydbname'
    };

    Y.namespace('mojito.models')[NAME] = {

        getData: function(selectcountry, callback) {
            var queryString = 'SELECT areaid, name FROM areas WHERE country="' + selectcountry + '" ORDER BY name';
            // mysqlConnection.query() will automaticly invoce mysqlConnection.connect()
            var mysqlConnection = mysqlClient.createClient(mysqlConfig);
            mysqlConnection.query(queryString, function selectCb(error, results, fields) {
                mysqlConnection.end();
                if (error) {
                    // NO connection is set
                    console.log(error.message);
                    callback(error, null);
                }
                else {
                    var queryString,
                        i,
                        mysqlConnectionsDeep = [],
                        stack = new Y.Parallel();
                    for (i=0; i<results.length; i++) {
                        queryString = 'SELECT * FROM cities WHERE areaid=' + results[i].aeraid + ' ORDER BY cityname';
                        mysqlConnectionsDeep[i] = mysqlClient.createClient(mysqlConfig);
                        mysqlConnectionsDeep[i].query(
                            queryString, 
                            stack.add(Y.rbind(function selectCb(errorDeep, resultsDeep, fieldsDeep, masterrecord, mastererror, index) {
                                mysqlConnectionsDeep[index].end();
                                if (errorDeep) {
                                    // NO connection is set
                                    console.log(error.message);
                                    mastererror = errorDeep;
                                }
                                else {
                                    // this.results is in fact the results of the first query
                                    masterrecord.cities = resultsDeep; 
                                }
                            }, this, results[i], error, i))
                        ); 
                    }           
                    stack.done(Y.bind(callback, null, error, results));
                }
            });            
        }

};

}, '0.0.1', {requires: ['parallel']});

I was afraid so...

But I'm not sure I understand how this could help.
Inside the second querycall, I'm at the deepest level. It would mean something like:
var self=this;
self.end(); straight afterwards.

Could you show me by modifying the code?

Regards,
Marco.