connect SQL in Node js

Question

var express = require('express');
var bodyParser = require("body-parser");
var app = express();
var sql = require("mssql");

// Body Parser Middleware
app.use(bodyParser.json());

//CORS Middleware
app.use(function (req, res, next) {
//Enabling CORS
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, contentType,Content-Type, Accept, Authorization");
next();
});



// config for your database
var config = {
user: 'sa',
password: 'abc@123',
server: 'MY-PC\\SQL',
database: 'dbStudent'
};
sql.close()
app.get('/GetTotalStudent', function (req, res) {
// connect to your database

sql.connect(config, function (err) {

if (err) console.log(err);

// create Request object
var request = new sql.Request();

// query to the database and get the records
request.query('select count(*) as totalrow from tblStudent', function (err, recordset) {

if (err) console.log(err)

// send records as a response
res.send(recordset.recordset[0]);
sql.close();
});
});
});

app.get('/GetCurrentData', function (req, res) {
// connect to your database

sql.connect(config, function (err) {

if (err) console.log(err);
var startpage = parseInt(req.query.Start);
var endpage = parseInt(req.query.End);
// create Request object
var request = new sql.Request();
var query = " SELECT * FROM ( SELECT ROW_NUMBER() OVER ( ORDER BY st_Id ) AS RowNum, * " +
" FROM tblStudent " +
" ) AS RowConstrainedResult " +
" WHERE RowNum >= " + startpage + " " +
" AND RowNum <= " + endpage + " " +
" ORDER BY RowNum";
// query to the database and get the records
request.query(query, function (err, recordset) {

if (err) console.log(err)

// send records as a response
res.send(recordset.recordsets);
sql.close();
});
});
});

//POST API
app.post("/addemployee", function(req , res){
var query = "INSERT INTO [tblEmployee] (firstname,lastname,email,password,birthdate,phonenumber,height,weight,gender) VALUES ('"+req.body.firstname+"','"+req.body.lastname+"','"+req.body.email+"','"+req.body.password+"','"+req.body.birthdate+"','"+req.body.phonenumber+"','"+req.body.height+"','"+req.body.weight+"','"+req.body.gender+"')"
executeQuery (res, query);
});
var server = app.listen(9090, function () {
console.log('Server is running..');
});