I have a function that connects to a sql database, queries it, formats the results into an html table and returns the html variable:
function getData() {
return new Promise((resolve, reject) => {
var sql = require("mssql");
var dbConfig = {
server: "server",
database: "db",
user: "user",
password: "pw"
}
var conn = new sql.Connection(dbConfig);
var req = new sql.Request(conn);
conn.connect(function (err) {
if (err) {
console.log(err);
reject(err);
return;
}
req.query("SELECT * FROM table",
(err, recordset) => {
// Here we call the resolve/reject for the promise
try {
// If the results callback throws exception, it will be caught in
// the catch block
resolve(resultsCallback(err, recordset));
}
catch (e) {
reject(e);
}
}
);
conn.close();
});
})
}
function resultsCallback(err, recordset) {
var tableify = require('tableify');
if (err) {
console.log(err);
throw err;
}
else {
var html = tableify(recordset);
html = html.replace('<table>', '');
html = html.replace('</table>', '');
return html;
}
};
And I am calling it like this:
getData().then((data)=>{console.log("Table data:",data);})
.catch((error)=>{console.log("ERROR LOADING SQL:",error);})
However, for some reason the output from this is: Table Data: undefined
I am unsure why this would be happening like this. Did I return the data correctly?
i think your resultsCallback is unnecessarily tangled up with error handling
i tried to clean up your example with some modern flair, hope it helps you out
const sql = require("mssql")
const tableify = require("tableify")
/**
* FORMAT RESULTS
* - format sql records as html
* - returns a string of html
*/
function formatResults(records) {
return tableify(records)
.replace("<table>", "")
.replace("</table>", "")
}
/**
* GET DATA
* - query records from a database
* - returns a promised string of html
*/
async function getData({db, table}) {
// open the sql connection pool
const pool = await sql.connect(db)
// query the database and format the results
try {
const results = await pool.request()
.input("tablename", table)
.query(`SELECT * from #tablename`)
return formatResults(results)
}
// rethrow query errors
catch (error) {
error.message = `getData sql query error: ${error.message}`
throw error
}
// always close the connection
finally {
pool.close()
}
}
// USAGE EXAMPLE BELOW
;(async() => {
const data = await getData({
db: {
server: "server",
database: "db",
user: "user",
password: "pw"
},
table: "table"
})
console.log(data)
})().catch(error => console.error(error))
Related
I'm having problems getting data from my AZURE SQL database. My code does get data, but not all of it. The intention is that the function needs to take all users in wicht the age is X (f.ex.:20)and return an array with those users. Right now the code just return the first user it finds on the database. I am using Azure-functions in which I use Insomnia to test the result.
Here is the function that gets the data from the DB:
function testfunc(age){
return new Promise ((resolve, reject) =>{
let result = [];
const sql = 'SELECT * FROM [datingschema].[user] where age = #age'
const request = new Request(sql, function(err){
if (err){
console.log("beforeerr");
console.log(err) //ingen err - så det godt nok!
console.log("aftererr");
reject(err);
}
})
request.addParameter('age', TYPES.Int, age)
request.on('row', (columns) => {
columns.forEach(column =>{
result.push(column.value)
})
resolve(result)
});
connection.execSql(request)
})
}
Here is a part of my code in Azure-function where I call for the function. There should be no errors in there as it works fine when I need to get only one user:
const db = require('../database/db');
module.exports = async function (context, req) {
context.log('JavaScript HTTP trigger function processed a request.')
try {
await db.startDb(); //start db connection
} catch (error) {
console.log("Error connecting to the database", error.message)
}
switch (req.method) {
case 'GET':
await get(context, req);
break;
case 'POST':
await post(context, req);
break
default:
context.res = {
body: "Please get or post"
};
break
}
}
async function get(context, req){
try{
let id = req.query.age
let user = await db.testfunc(id)
context.res = {
body: user
};
} catch(error){
context.res = {
status: 400,
body: `No User - ${error.message}`
}
}
}
The error happens, because you resolve your promise after you have read the first row. Consider the following:
function testfunc(age){
return new Promise ((resolve, reject) =>{
let result = [];
const sql = 'SELECT * FROM [datingschema].[user] where age = #age'
const request = new Request(sql, function(err){
if (err){
console.log("beforeerr");
console.log(err) //ingen err - så det godt nok!
console.log("aftererr");
reject(err);
}
})
request.addParameter('age', TYPES.Int, age)
// This is executed multiple times, once for each row
request.on('row', (columns) => {
let row = []
// Accumulate the columns to a row
columns.forEach(column =>{
row.push(column.value)
})
// Don't resolve here. Instead append to result..
// resolve(result)
result.push(row)
});
// This is executed once, when the query has completed
request.on('done', () => {
// .. and resolve here
resolve(result)
})
connection.execSql(request)
})
}
Please help me, I need to implement a function in a separate module file and in the route where the render has to call this function receiving the query data:
function getSobre() {
return new Promise((resolve, reject) => {
db.query(`SELECT * FROM sobre ORDER BY cod DESC LIMIT 1`, (err, results) => {
if (err) {
return reject(err);
} else {
return resolve(results);
}
});
});
}
const data = {
title: getSobre().then(data => {
/*
* HERE How do I return this "data" to the "title:" ?????????????
*/
}),
name: 'Fabio',
profession: 'Analista'
}
module.exports = data;
db.query is a Js callback . Which will wait for the result , then return anything.
So data will always be empty since it is getting returned much before db.query getting full resolved
You should wrap this in a native promise, and then resolve the promise :
function getTabela{
return new Promise(function(resolve, reject) {
// The Promise constructor should catch any errors thrown on
// this tick. Alternately, try/catch and reject(err) on catch.
let sql = "SELECT * FROM sobre ORDER BY cod DESC LIMIT 1";
var data = {};
db.query(sql, (err, results, fields) => {
if (results.length > 0) {
resolve(fields)
} else {
console.log('Erro: ' + err);
}
});
});
}
getTabela().then(function(rows) {
// now you have your rows, you can see if there are <20 of them
}).catch((err) => setImmediate(() => { throw err; }));
This way you should always have the data which is expected out of the query.
My problem is, I want to make INSERT query for every object from JSON using some loop, but I almost always got an error "Cannot set headers after they are sent to the client".Can someone help?Tnx
const connection = require('./config');
module.exports.excel = function (req, res) {
var _query = 'INSERT INTO excel (id, first_name, last_name) values ?';
var jsonData = req.body;
var values = [];
function database() {
return new Promise((resolve, reject) => {
jsonData.forEach((value) => {
values.push([value.id, value.first_name, value.last_name]);
connection.query(_query, [values], (error, results) => {
if (error) {
reject(
res.json({
status: false,
message: error.message
}))
} else {
resolve(
res.json({
status: true,
data: results,
message: 'Excel file successfully created in database'
}))
}
});
});
})
}
async function write() {
await database();
}
write();
}
After I got JSON from my Angular 6 front I put req.body into jsonData and try with forEach to put every object("value" in this case) into query and write that into Excel file.
You will have to wrap each query in a Promise and wait for all to complete before sending the response using Promise.all
Not that database() is going to throw when one of the queries fail and you won't have any access to the resolved promises.
const connection = require('./config');
module.exports.excel = function(req, res) {
const _query = 'INSERT INTO excel (id, first_name, last_name) values ?';
const jsonData = req.body;
function database() {
return Promise.all(
jsonData.map(
value =>
new Promise((resolve, reject) => {
const values = [value.id, value.first_name, value.last_name]
connection.query(_query, [values], (error, results) => {
if (error) {
reject(error.message);
return;
}
resolve(results);
});
})
)
);
}
async function write() {
try {
const results = await database();
res.json({
status: true,
data: results,
message: 'Excel file successfully created in database'
});
} catch (e) {
res.json({
status: false,
message: e.message
});
}
}
write();
};
A file contains json data with details of database.
For each database connection, a series of queries need to be executed.
Currently, the map function is waiting for the database connection.
Below is the start function
function start() {
console.log('function initiated');
try {
let jsonData = fs.readFileSync('../request.json');
let jsonString = JSON.parse(jsonData);
//jsonString['request'].forEach(async function(json) {
jsonString['request'].map(async json => {
dbdetails = json.dbdetails;
//dbdetails.forEach(async function(db){
await dbbdetails.map(async db => {
console.log('pdbdetails: ' + db);
connString = json.connString;
//makes the DB connection
await connectDB(db.userId, db.Password, connString)
.then(async conn => {
await execution(conn, pdbDetails, vmUser, vmPassword, ip);
})
.catch(err => {
console.log(err);
});
console.log('after each execution');
//}
});
});
} catch (err) {
console.log(err.message);
return;
}
}
Below function is to make a database connection and return the connection
function connectDB(oUser, oPassword, connString) {
console.log('inside connectDB');
return new Promise((resolve, reject) => {
oracledb.getConnection(
{
user: oUser,
password: oPassword,
connectString: connString
},
function(err, connection) {
if (err) {
console.error(err.message);
reject(err);
//throw err;
}
console.log('returning connection');
//console.log(connection);
resolve(connection);
//return connection;
}
);
});
}
below is the function which executes servies of queries on database
function execution() {
/// series of sql query execution
}
Not sure what you’re trying to do exactly, but sounds like the problem is that .map doesn’t wait for your async functions. If you have to do them one at a time, use a for loop:
for ( var item of array ) {
await item.something();
}
To do them all at once:
var results = await Promise.all( array.map( item => item.something() )
I use express and PostgreSql.
My Project Folder :
-Model
-Visitor.js
-app.js
I have connected postgresql with pg and i've tested with a query. It's running well. But, there is a query on Visitor.js file.
var visitor = function() {
this.add = function() {
var ret = false;
db.query({text: 'INSERT INTO visitor(visitorid, data, status) VALUES($1, $2, $3)', values:[id, JSON.stringify(data), "1"]}, function (err, response) {
if(!err) {
ret = true;
}
});
return ret;
}
}
This query always inserts a row in my table but returns false. This function should wait query to end. How can i do it ?
You should await on a promise
this.add = function() {
return new Promise((resolve, reject) => {
db.query({text: 'INSERT INTO visitor(visitorid, data, status) VALUES($1, $2, $3)', values:[id, JSON.stringify(data), "1"]}, function (err, response) {
if(!err)
resolve(response)
else
reject(err)
});
})
}
Then you can await on visitor.add function
EDIT
If you are using the pg library: as shown in Getting Started, you can directly await on the client.query function as it returns a Promise when you don't provide a callback
const { Client } = require('pg')
const client = new Client()
await client.connect()
const res = await client.query('SELECT $1::text as message', ['Hello world!'])
console.log(res.rows[0].message) // Hello world!
await client.end()