How to execute two mysql queries using promise in nodejs? - mysql

Question

Here is what i going to achieve, i want to have an JSON data that returned from my node.js server is joined based on the value of first mysql queries (array JSON data)
if i just want to execute two mysql queries i just enable multipleStatements: true then the code will be like this :
app.post('/product', function (req, res) {
connection.query('call getProductList; call rowCountTotal', function (err, rows, fields) {
if (!err) {
var response = [];
if (rows.length != 0) {
response.push({ 'result': 'success', 'data': rows });
} else {
response.push({ 'result': 'error', 'msg': 'No Results Found' });
}
res.setHeader('Content-Type', 'application/json');
res.status(200).send(JSON.stringify(response));
} else {
res.status(400).send(err);
}
});
});
than the data will showed up two JSON that are separated in two arrays, but what i want to build here is one JSON with multiple array JSON data, which is looked like this :
Sample JSON that i want :
[
{
"product_id":"1",
"product_name":"MX-001",
"product_attachment":[
{
"product_id":"1",
"product_attachment_id":"1",
"file_name":"maxgrand5.jpg",
"file_path":"assets"
}
]
}
]
And here is what i trying to do in my node.js server side code, i trying to use
Promise.all (i think this code i should use right?) :
return new Promise(function(resolve, reject) {
Promise.all(connection.query('call getProductSingle("'+ product_series +'")', function (err, rows, fields) {
if (!err) {
var response = [];
if (rows.length != 0) {
response.push({ 'result': 'success', 'data': rows });
} else {
response.push({ 'result': 'error', 'msg': 'No Results Found' });
}
connection.query('call getProductAttachment("'+ rows[0][0].product_id +'")', function (err, rowsAttachment, fields) {
if (!err) {
console.log("second query");
if (rowsAttachment.length != 0) {
response.push({'product_attachment': rowsAttachment });
} else {
response.push({ 'result': 'error', 'msg': 'No Results Found' });
}
}
});
console.log("outside second query");
res.setHeader('Content-Type', 'application/json');
res.status(200).send(JSON.stringify(response));
} else {
res.status(400).send(err);
}
console.log("last");
if (err) {
return reject(err);
}
resolve(res);
}));
});
here is my Stored Procedure result which named in 'getProductSingle' :
product_id = 1
product_name = MX-001
and here is my second procedure result 'getProductAttachment' :
product_id = 1
file_name = maxgrand5.jpg
file_path = assets
product_attachment_id = 1
one single product_id can have more than 1 product_attachment_id
how can i get the data joined?
I just updated my question, the problem is the second query is too late when i make the request, i should use promise to make it not late, how to do this?

Answer 1

First I created the query, in which the product_single table is joined to the product_attachments, maybe you want to restrict it with an WHERE clause or a paging mechanism with LIMIT and OFFSET:
SELECT ps.product_id, ps.product_name, pa.product_attachment_id,
pa.file_name, pa.file_path
FROM product_single ps
LEFT JOIN product_attachment pa
ON ps.product_id = pa.product_id
ORDER by ps.product_id,pa.product_attachment_id;
In the following code I will refer to this query with a call product_join_att.
return new Promise(function(resolve, reject) {
var result_products = [];
var result_attachments = [];
var old_id = undefined;
var old_name = undefined;
var new_id = undefined;
var row_index = 0;
connection.query('call product_join_att', function (err, rows, fields) {
if (err) {
reject(err);
return;
} else if (rows.length == 0) {
reject(new Error('No Results found'));
return;
}
while (row_index < rows.length ) {
new_id = rows[row_index].product_id;
if (old_id !== new_id) { // any new line with an new id...
if (typeof old_id !== 'undefined') { // when the old line is existing
result_products.push( // push the product
{"product_id": old_id.toString(),
"product_name":old_name,
"product_attachment": result_attachments
});
}
old_id = new_id; // remember the new_id
old_name = rows[row_index].product_name;// and name
product_attachments = []; // and initialize attachments.
}
product_attachments.push({ // provide the inner attachment informations.
"product_id": new_id,
"product_attachment_id" : rows[row_index].product_attachment_id,
"file_name" : rows[row_index].file_name;
"file_path" : rows[row_index].file_path;
});
row_index++; // and go to the next row.
}
if (typeof old_id !== 'undefined') { // if there are still data
result_products.push( // push the last line also.
{"product_id": old_id.toString(),
"product_name":old_name,
"product_attachment": result_attachments
});
}
} // query
resolve(result_products);
} // end of promise...

Answer 2

i figure it out with simplier solution but this way is not a "promise" way to get it done, so decide it which to use if you guys face the problem like this. Since i dont need many data to loop, just a single root array JSON with one dimension JSON array, i will just put it this way :
app.post('/getsingleproduct', function (req, res) {
var product_series = req.body.product_series;
connection.query('call getProductSingle("'+ product_series +'")', function (err, rows, fields) {
if (!err) {
var response = [];
if (rows.length != 0) {
response.push({ 'result': 'success', 'data': rows[0] });
} else {
response.push({ 'result': 'error', 'msg': 'No Results Found' });
}
connection.query('call getProductAttachment("'+ rows[0][0].product_id +'")', function (err, rowsAttachment, fields) {
if (!err) {
if (rowsAttachment.length != 0) {
response[0].data[0]['product_attachment']= rowsAttachment[0];
res.setHeader('Content-Type', 'application/json');
res.status(200).send(JSON.stringify(response));
} else {
response.push({ 'result': 'error', 'msg': 'No Results Found' });
res.status(400).send(err);
}
}
});
} else {
res.status(400).send(err);
}
});
});
this is a non-promise way, if you need promise way, look for #Myonara answer, i think that the best