old_contents: 'use strict';
  
  require('dotenv').config();
  const Pg = require('pg');
  
  const MEASUREMENTS_TABLE = process.env.MEASUREMENTS_TABLE;
  const STATION_IDS_TABLE = process.env.STATION_IDS_TABLE;
  
  const pg = new Pg.Client({
      connectionString: process.env.DATABASE_URL,
      ssl: true
  });
  
  pg.connect();
  
  const measurementsTable = pg.query(`CREATE TABLE ${MEASUREMENTS_TABLE}(timestamp TIMESTAMP NOT NULL, station_id VARCHAR(12) NOT NULL, is_occupied BOOL NOT NULL, distance INT NOT NULL)`)
      .then(result => console.log(`${MEASUREMENTS_TABLE} created`))
      .catch(error => console.log(error));
  
  
  const stationIdsTable = pg.query(`CREATE TABLE ${STATION_IDS_TABLE}(station_id VARCHAR(12) NOT NULL)`)
      .then(result => console.log(`${STATION_IDS_TABLE} created`))
      .catch(error => console.log(error));
  
  Promise.all([measurementsTable, stationIdsTable]).then(values => pg.end());
new_contents: 'use strict';
  
  require('dotenv').config();
  const Pg = require('pg');
  
  const MEASUREMENTS_TABLE = process.env.MEASUREMENTS_TABLE;
  const STATION_IDS_TABLE = process.env.STATION_IDS_TABLE;
  
  const pg = new Pg.Client({
      connectionString: process.env.DATABASE_URL,
      ssl: true
  });
  
  pg.connect();
  
  const measurementsTable = pg.query(`CREATE TABLE ${MEASUREMENTS_TABLE} (timestamp TIMESTAMP NOT NULL PRIMARY KEY, station_id VARCHAR(12) NOT NULL, is_occupied BOOL NOT NULL, distance INT NOT NULL)`)
      .then(result => console.log(`${MEASUREMENTS_TABLE} created`))
      .catch(error => console.log(error));
  
  
  const stationIdsTable = pg.query(`CREATE TABLE ${STATION_IDS_TABLE}(station_id VARCHAR(12) NOT NULL)`)
      .then(result => console.log(`${STATION_IDS_TABLE} created`))
      .catch(error => console.log(error));
  
  Promise.all([measurementsTable, stationIdsTable]).then(values => pg.end());
subject: Add primary key while creating tables