Heroku_database_deploy.js

// conneect to database
heroku addons:add heroku-postgresql:dev

// add dependcy
"dependencies": {
    "pg": "2.x",
    "express": "~4.9.x",
    "cool-ascii-faces": "~1.3.x"
}

// add to your app
var pg = require('pg');
app.get('/db', function (request, response) {
  pg.connect(process.env.DATABASE_URL, function(err, client, done) {
    client.query('SELECT * FROM test_table', function(err, result) {
      done();
      if (err)
       { console.error(err); response.send("Error " + err); }
      else
       { response.send(result.rows); }
    });
  });
})

// make a sample database base in console
heroku pg:psql
psql (9.3.2, server 9.3.3)
SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
Type "help" for help.
=> create table test_table (id integer, name text);
CREATE TABLE
=> insert into test_table values (1, 'hello database');
INSERT 0 1
=> \q