Develop Reference

Render my ejs file after my query finishes

I want to make sure that my application will only call res.render('pages/students' ...) after all my queries finishes and I get all the necessary data. However, I completely have no clue how to do this at all and I am having trouble applying all the examples I see online onto my code. Can someone give me a hand? (There are two con.query(...) in my route. I want to only render('pages/students'...) after both of these con.query completely finishes. Therefore, I am using async to run all my queries to completion. However now for some reason my page wont event load.
app.get('/admin', function(req, res) {
var sql =
'SELECT events.id, name, description, MONTHNAME(start_time) AS month, DAY(start_time) AS day, ' +
"YEAR(start_time) AS year, DATE_FORMAT(start_time, '%h:%i%p') AS start_time, HOUR(start_time) AS start_hour, MINUTE(start_time) AS start_minute, " +
"DATE_FORMAT(end_time, '%h:%i%p') AS end_time, HOUR(end_time) AS end_hour, MINUTE(end_time) AS end_minute, location, max_capacity, hidden_sign_up, " +
'eventleaders.first_name AS eventLeader FROM events LEFT JOIN eventleaders_has_events ON events.id = eventleaders_has_events.events_id ' +
'LEFT JOIN eventleaders ON eventleaders_has_events.eventleaders_id = eventleaders.id;';
var events = {};
con.query(sql, function(err, results) {
if (err) throw err;
async.forEachOf(results, function(result, key, callback) {
var date = result.month + ' ' + result.day + ', ' + result.year;
var other = 'N/A';
if (result.other !== null) {
other = result.other;
}
if (typeof events[date] === 'undefined') {
events[date] = {};
}
var studentAttendees = {};
var sql =
'SELECT * FROM students INNER JOIN students_has_events ON students.id = students_has_events.Students_id ' +
'WHERE students_has_events.Events_id = ?';
var values = [result.id];
con.query(sql, values, function(err, results1) {
if (err) throw err;
async.forEachOf(results1, function(result1, key, callback) {
studentAttendees[result1.first_name + ' ' + result1.last_name] = {
netID: result1.netID,
phoneNumber: result1.phone,
email: result1.email
};
});
//still need to get the event leader attendees
events[date][result.name] = {
startTime: result.start_time,
location: result.location,
endTime: result.end_time,
description: result.description,
eventLeader: result.eventLeader,
numberRegistered: result.hidden_sign_up,
maxCapacity: result.max_capacity,
poster: '/images/sample.jpg',
other: other,
attendees: studentAttendees
};
});
});
});
});

Two options:
app.get('/admin', function(req, res) {
...
con.query(sql, function(err, result) {
...
con.query(sql, values, function(err, result) {
events[date][currRecord.name] = {
...
};
// put it here
console.log(events);
res.render('pages/admin', {
events: events
});
});
}
});
});
Or use the Promise version of mysql
const mysql = require('mysql2/promise');
// make this async
app.get('/admin', async function(req, res) {
try {
...
// might want to move this elsewhere inside async function
const con = await mysql.createConnection({host:'localhost', user: 'root', database: 'test'});
const result1 = await con.query(sql);
// run your logic preferably inside map
// result2 is an array of Promises
const result2 = result1.map((result, index) => {
var currRecord = result[index];
var date =
currRecord.month + ' ' + currRecord.day + ', ' + currRecord.year;
var other = 'N/A';
if (currRecord.other !== null) {
console.log('here');
other = currRecord.other;
}
if (typeof events[date] === 'undefined') {
events[date] = {};
}
//get all the student attendees of this event
var studentAttendees = {};
var sql =
'SELECT * FROM students INNER JOIN students_has_events ON students.id = students_has_events.Students_id ' +
'WHERE students_has_events.Events_id = ?';
var values = [currRecord.id];
return con.query(sql)
})
// result3 is an array of results. If your results is also an array, the structure might look lik [[student], [student]] etc.
const result3 = await Promise.all(result2);
// run your logic to get events
console.log(events);
res.render('pages/admin', {
events: events
});
} catch (e) {
// handle error
console.error(e)
}
});

Syntax Error when using multiple parameter substitutions in a MYSQL Query

I need to Update MYSQL data using JS after I receive an AJAX Post request
I made a variable for the MYSQL Update Query and I'm passing in the field to be updated, new value, row to be updated as an array. But for some reason those variables are read with single quotes(') which, I believe, is causing me a syntax error.
var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var MYSQL = require('mysql');
var server = require('http').createServer(app);
//declaring var 'conn' for MYSQL.createPool
let columns = new Array();
// Piece of code Starting the Server
// Routing
app.use(bodyParser.json()); // for parsing application/json
app.use(bodyParser.urlencoded({ extended: true })); // for parsing application/x-www-form-urlencoded
app.use(express.static(path.join(__dirname, 'public')));
app.post('/', function (req, res) {
updateWorkbook(req.body);
res.send('Thanks for the data.');
});
//This is the function extracts the row, field value that need to be updated from the AJAX request
function updateWorkbook( data ){
getcolumns().then( function (columns) {
console.log("Columns got returned to Updateworkbook function")
for (let d = 0; d < data.length; d++) {
let rowToUpdate = data[d].id.replace('row_', '').split('_')[0];
let fieldToUpdate = data[d].id.replace('row_', '').split('_')[1];
let newValue = data[d].value;
console.log('row,field,value: ' + rowToUpdate + '|' + fieldToUpdate + '|' + newValue);
let key_to_replace;
for(let i = 0; i < columns.length; i++) {
let looper = columns[i].toLowerCase()
if (looper === fieldToUpdate) {
key_to_replace = columns[i]
}
}
let field_to_replace = key_to_replace.toString();
console.log(field_to_replace) //It prints out a normal string value here
updatemysql(field_to_replace, newValue, rowToUpdate);
}
});
};
//This is the function which updates MYSQL data
function updatemysql(field, newval, row) {
var sql = "UPDATE mydb.mytable SET ? = ? WHERE ROW_ID = ?;";
conn.getConnection( function (err, connection) {
if (err){
return cb(err);
connection.release();
}
console.log("Connection got established")
conn.query(sql, [field, newval, row], function (error, results){
if (error){
throw error;
connection.release();
}
console.log('Data Updated');
connection.release();
});
});
}
//Function to extract all columns from MYSQL and stores them in an array
function getcolumns() {
return new Promise(function(resolve, reject) {
console.log("getcolumns got initiated")
conn.getConnection( function (err, connection) {
if (err){
return cb(err);
connection.release();
return reject(err);
}
else {
var sql = "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'mydb' AND TABLE_NAME = 'mytable';"
conn.query(sql, function (error, results){
for (let i = 0; i < results.length; i++) {
columns.push(results[i]['COLUMN_NAME'])
}
resolve(columns);
console.log("Extracted columns")
connection.release();
});
}
});
});
};
Here's the error I receive:
Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''Source_of_Phone_Number_' = 'Test' WHERE ROW_ID = '1'' at line 1`
Source_of_Phone_Number_ is the key_to_replace.
Test is the newValue.
1 is the Row_ID.

There is a problem in function updatemysql(), which uses the following SQL :
var sql = "UPDATE mydb.mytable SET ? = ? WHERE ROW_ID = ?;";
You cannot pass a column name as a parameter.
You would need to change this to :
var sql = "UPDATE mydb.mytable SET " + field + " = ? WHERE ROW_ID = ?;";
Accordingly, only two parameters should be passed to the query :
conn.query(sql, [newval, row], function (error, results){ ... });

how to call an array which is in a function from the another function in javascript?

This is the async function:
async function getpackages(conn, childId, callback) {
var childId = childId;
var request6 = new sql.Request(conn);
var packageQuery = "select OrderId,ChildID from dbo.tbl_Scheduler where NoOfMealsLeft>0 and ChildId=" + childId;
await request6.query(packageQuery, function (err, packagelist) {
if (!err && packagelist.recordsets.length > 0) {
console.log("Error:" + err + "Result:" + util.inspect(packagelist.recordsets[0]));
var orderdetail_ = [];
for (i = 0; i < packagelist.recordsets[0].length; i++) {
orderdetail_.push(packagelist.recordsets[0][i].OrderId);
}
console.log("-->" + orderdetail_);
callback(null, packagelist.recordsets[0]);
} else if (packagelist.recordsets.length < 1) {
callback("Not a valid id input", null);
}
});
};
I need to call the orderdetails_ array in the query. The array contains four data and I need to iterate over 4 data one by one, using the or in the SQL query.
module.exports.newscheduledmeal = function (req, res, next, callback) {
let entered_date = req.query.date;
let childId = req.query.id;
let current_date = new Date().toISOString().slice(0, 10);
if (entered_date < current_date) {
return callback('Please enter date more than or equal to current date.', null);
} else
var conn = new sql.ConnectionPool(dbConfig);
try {
conn.connect().then(function () {
var request = new sql.Request(conn);
getpackages(conn, childId, function (err, orderid) {
if (err) {
callback(err, null);
} else
var PackageidQuery = "select PackageId from dbo.tbl_Order where OrderId=";
request.query(PackageidQuery, function (err, packagelist) {
if (!err) {
conn.close();
callback(null, packagelist.recordsets);
} else {
conn.close();
callback("Error", null);
}
});
});
});
} catch (err) {
console.log("Exception occured:" + err);
conn.close();
callback(err, null);
}
};
I want to get the details of the array which is in getpackages to be used in the module section and specifically in the SQL query section.

TypeError: Cannot read property 'toString' of undefined - why?

Here is the line (50) where this is happening:
var meetingId = meeting._id.toString(),
And here is the full, relevant code:
var MongoClient = require('mongodb').MongoClient;
var assert = require('assert');
var ObjectId = require('mongodb').ObjectID;
var config = require('./config'),
xlsx = require('./xlsx'),
utils = require('./utils'),
_ = require('lodash'),
url = config.DB_URL;
var meetings = [];
function findNumberOfNotesByMeeting(db, meeting, callback) {
var meetingId = meeting._id.toString(),
meetingName = meeting.name.displayValue,
attendees = meeting.attendees;
host = meeting.host;
var count = 1, pending = 0, accepted = 0;
console.log("==== Meeting: " + meetingName + '====');
_.each(attendees, function(item) {
console.log(count++ + ': ' + item.email + ' (' + item.invitationStatus + ')');
if (item.invitationStatus == 'pending') { pending++; }
else if (item.invitationStatus == 'accepted') { accepted++; }
});
console.log("*** " + attendees.length + ", " + pending + "," + accepted);
db.collection('users').findOne({'_id': new ObjectId(host)}, function(err, doc) {
var emails = [];
if (doc.emails) {
doc.emails.forEach(function(e) {
emails.push(e.email + (e.primary ? '(P)' : ''));
});
}
var email = emails.join(', ');
if (utils.toSkipEmail(email)) {
callback();
} else {
db.collection('notes').find({ 'meetingId': meetingId }).count(function(err, count) {
if (count != 0) {
console.log(meetingName + ': ' + count + ',' + attendees.length + ' (' + email + ')');
meetings.push([ meetingName, count, email, attendees.length, pending, accepted ]);
}
callback();
});
}
});
}
function findMeetings(db, meeting, callback) {
var meetingId = meeting._id.toString(),
host = meeting.host;
db.collection('users').findOne({'_id': new ObjectId(host)}, function(err, doc) {
var emails = [];
if (!err && doc && doc.emails) {
doc.emails.forEach(function(e) {
emails.push(e.email + (e.primary ? '(P)' : ''));
});
}
var email = emails.join(', ');
if (utils.toSkipEmail(email)) {
callback();
} else {
db.collection('notes').find({ 'meetingId': meetingId }).count(function(err, count) {
if (count != 0) {
var cursor = db.collection('meetings').find({
'email': {'$regex': 'agu', '$options': 'i' }
});
}
callback();
});
}
cursor.count(function(err, count) {
console.log('count: ' + count);
var cnt = 0;
cursor.each(function(err, doc) {
assert.equal(err, null);
if (doc != null) {
findNumberOfNotesByMeeting(db, doc, function() {
cnt++;
if (cnt >= count) { callback(); }
});
}
});
});
});
}
MongoClient.connect(url, function(err, db) {
assert.equal(null, err);
findMeetings(db, function() {
var newMeetings = meetings.sort(function(m1, m2) { return m2[1] - m1[1]; });
newMeetings.splice(0, 0, [ 'Meeting Name', 'Number of Notes', 'Emails' ]);
xlsx.writeXLSX(newMeetings, config.xlsxFileNameMeetings);
db.close();
});
});
As you can see, the meeting variable (which I am almost 100% sure is the problem, not the _id property) is passed in just fine as a parameter to the earlier function findNumberOfNotesByMeeting. I have found some information here on SO about the fact that my new function may be asynchronous and needs a callback, but I've attempted to do this and am not sure how to get it to work, or even if this is the right fix for my code.

You're not passing the meeting object to findMeetings, which is expecting it as a second parameter. Instead of getting the meeting object, the function receives the callback function in its place, so trying to do meeting._id is undefined.
In fact, what is the purpose of the findMeetings function? It's name indicates it can either find all meetings in the database, or all meetings with a specific id. You're calling it without a meeting id indicating you might be trying to find all meetings, but its implementation takes a meeting object. You need to clear that up first.

nested sql queries inside for loop node.js not working

I have a for loop going through a JSON array - with help from this stack question
Whilst looping the script does the following:
- Does the JSON item exist in the tables?
- if yes
- Is the data different?
- if yes
- Update
- if no
- Do nothing
- if no
-insert into database
I found this question which allowed me to query on each for loop so I am able to get the names from the JSON and query them correctly :
for(var i=0; i<content.prices.length; i++) {
var price = content.prices[i].price
var itemName = content.prices[i].market_hash_name;
var q = "SELECT * FROM prices WHERE item = ?";
(function() {
var iNameCopy = itemName;
var priceCopy = price;
connection.query(q, iNameCopy, function (err, results) {
if (err) throw err;
if(results.length === 1) {
logger.info(iNameCopy + " does exist");
}
else if (results.length === 0){
logger.info(iNameCopy + " does not exist");
}
});
}());
}
Moving onto adding the if statement inside results.length === 1
for(var i=0; i<content.prices.length; i++) {
var price = content.prices[i].price
var itemName = content.prices[i].market_hash_name;
var q = "SELECT * FROM prices WHERE item = ?";
(function() {
var iNameCopy = itemName;
var priceCopy = price;
connection.query(q, iNameCopy, function (err, results) {
if (err) throw err;
if(results.length === 1) {
if(parseFloat(results[0].current_price) != parseFloat(priceCopy)) {
logger.info(iNameCopy + " does exist with old price: " + results[0].current_price + " and new price: " + priceCopy);
}
}
else if (results.length === 0){
logger.info(iNameCopy + " does not exist");
}
});
}());
}
Again this is still working.
Now finally replacing those loggers with new sql queries is where the code stumbles. The for loop runs as if I keep the loggers they display however the sql query loggers do not display:
I tried both this way I found from the other stack question and without wrapping it in a function but neither worked. Any suggestions?
for(var i=0; i<content.prices.length; i++) {
var price = content.prices[i].price
var itemName = content.prices[i].market_hash_name;
var q = "SELECT * FROM prices WHERE item = ?";
(function() {
var iNameCopy = itemName;
var priceCopy = price;
connection.query(q, iNameCopy, function (err, results) {
if (err) throw err;
if(results.length === 1) {
if(parseFloat(results[0].current_price) != parseFloat(priceCopy)) {
var sql2="UPDATE `prices` SET `current_price` = ?, `timeStamp` = ? WHERE `item` = ?";
(function() {
var iNameCopy2 = iNameCopy
var priceCopy2 = priceCopy
connection.query(sql2, [priceCopy2, 'Now()', iNameCopy2], function(err,results){
logger.info("UPDATE: " + iNameCopy2 + ' has been updated with price ' + priceCopy2);
});
}());
}
}
else if (results.length === 0){
var sql3="INSERT INTO `prices` (`item`, `current_price`, `timeStamp`) VALUES (?, ?, ?)";
(function() {
var iNameCopy3 = iNameCopy
var priceCopy3 = priceCopy
connection.query(sql3, [iNameCopy3, priceCopy3, 'Now()'], function(err,results){
logger.info("INSERT: " + iNameCopy3 + ' has been added with price ' + priceCopy3);
});
}());
}
});
}());
}
note: I have my database connection on the outside of the for loop:
var connection = mysql.createConnection(db_access);
connection.connect(function(err){
if(err){
logger.error('Error connecting to Db');
return;
}
});