Access Multiple table concurrently Mysql Nodejs - mysql

Question

I am trying to assing a structured array from two tables, First table select query from which the value in result fetch the ID and assing to the next query, Here is my code
var query = db.query('select * from orderdish'),
users = [];
query
.on('error', function(err)
{
console.log(err);
updateSockets(err);
})
.on('result', function(order,callback)
{
order.abc ='11';
order.OrderKOT=[];
var queryOrderKOT = db.query('select * from tblorderkot where order_Id='+ order.order_Id,function()
{
kotOrders = [];
queryOrderKOT
.on('error',function(err)
{
console.log(err);
updateSocket(err);
})
.on('result',function(orderKOT)
{
kotOrders.push(orderKOT);
})
.on('end', function()
{
console.log(kotOrders);
order.OrderKOT.push(kotOrders);
});
});
console.log(order);
users.push(order);
/* aa(function(){
});*/
})
.on('end', function()
{
// loop on itself only if there are sockets still connected
if (connectionsArray.length)
{
pollingTimer = setTimeout(pollingLoop, POLLING_INTERVAL);
console.log("This is End Values");
updateSockets({ users: users });
}
});
It's setting order.OrderKOT to empty. I know the it got to be done with call back in query.on(result) but if I set it's not fetching me any result. Second Query queryOrderKOT is working but it's fetching value pretty late and it's not pusing value to order.OrderKOT. Suggesst me for fetching the value concurrently.

Answer 1

It is likely that the "end" event for the first query is occurring before the second queryOrderKot query has had a chance to complete.
You should experience the expected behavior if you move the main response logic from the "end" of query to the "end" or "result" of queryOrderKot.

Answer 2

After so much of head breaking finally found the solution for concurrent mysql nodejs check #kevin Reilly thanks for trying a lot. I found out what ever we tried was streaming query. Which will be do the process async. Now coming back to the callback I wrote following and it's working perfectly
var query = db.query('select * from orderdish', function (err, results, fields, callback) {
if (err) {
console.log("ERROR: " + err.message);
updateSockets(err);
}
else {
// length of results
var count = 0;
// pass the db object also if you wanna use the same instance
q2(count, results, callback);
}
});
function q2(count, results, callbacks) {
var queryOrderKOT = db.query('select * from tblorderkot where order_Id=' + results[count].order_Id, function (err, resultKOT, KOTFields, callback) {
console.log(resultKOT);
results[count].OrderKOT = resultKOT;
count++;
if (count < results.length) {
q2(count, results, callback);
}
else {
// do something that you need to do after this
console.log(results);
//callbacks(results);
}
});
}

Answer 3

Here is my whole Code,
var mysql = require('mysql')
var io = require('socket.io').listen(3000)
var db = mysql.createConnection({
host: 'localhost',
user: 'root',
password: 'vsk',
database: 'hahaha'
})
var POLLING_INTERVAL = 3000, connectionsArray = [], pollingTimer;
db.connect(function (err) {
if (err) console.log(err)
})
var socketCount = 0, restID = 0;
var pollingLoop = function () {
var query = db.query('select * from orderdish'), users = [];
.on('error', function (err) {
console.log(err);
updateSockets(err);
}).on('result', function (order) {
console.log("THis is USerID" + order.order_Id);
order.abc = '11';
order.OrderKOT = [];
var queryOrderKOT = db.query('select * from tblorderkot where order_Id=' + order.order_Id);
kotOrders = [];
queryOrderKOT.on('error', function (err) {
console.log(err);
updateSocket(err);
}).on('result', function (orderKOT) {
kotOrders.push(orderKOT);
query.on('end', function () {
console.log("This is at end values");
// loop on itself only if there are sockets still connected
if (connectionsArray.length) {
pollingTimer = setTimeout(pollingLoop, POLLING_INTERVAL);
console.log("This is End Values");
updateSockets({
users: users
});
}
});
}).on('end', function () {
console.log(kotOrders);
console.log("This is my KOT End");
order.OrderKOT.push(kotOrders);
users.push(order);
console.log(users);
//callback(kotOrders);
});
console.log(order);
});
};
io.sockets.on('connection', function (socket) {
console.log("New Connection Opened");
socket.on('restID', function (restIDs) {
console.log(restIDs);
restID = restIDs;
console.log('Number of connections:' + connectionsArray.length);
if (connectionsArray.length > 0) {
console.log("Here is the Pooling Loop");
pollingLoop();
}
});
socket.on('disconnect', function () {
var socketIndex = connectionsArray.indexOf(socket);
console.log('socket = ' + socketIndex + ' disconnected');
if (socketIndex >= 0) {
connectionsArray.splice(socketIndex, 1);
}
});
connectionsArray.push(socket);
});
var updateSockets = function (data) { // adding the time of the last update data.time = new Date();
// sending new data to all the sockets connected connectionsArray.forEach(function(tmpSocket) {
// tmpSocket.volatile.emit('notification', data); console.log(data); tmpSocket.volatile.emit('notification', data); }); };