In the previous chapter, we executed all our queries in a file called .sqlite.db. We will use this same file to demonstrate how to execute queries and receive their results inside our node process:

    /**
     * Import the SQLite library, and initialize the SQLite db
    instance
     * Mention the location of the ".sqlite.db" file that you 
    used in the previous chapter
     * We want the absolute path of the file, for better
      clarity, hence, the use of path.resolve
     * The location inside path.resolve, is the location of the 
     sqlite.db file relative to this one
    */
    const sqlite3 = require('sqlite3')
    const path = require('path')
    const db = new 
      sqlite3.Database(path.resolve('./.sqlite.db'))

   /**
     * The "serialize" method of the db instance makes sure
      that all queries directly in its callback are executed 
    sequentially
     */
    db.serialize(function () {
      /**
       * db.run is used to execute write queries (UPDATE,
     CREATE and DELETE).
       * Since this is called inside the "serialize" callback,
     it will be executed in series, and a callback is not 
     required.
       */
      db.run('UPDATE temperature SET value=21.3 WHERE 
     createdAt="2017-06-24 10:27:25"')
      /**
       * The "all" method of the db instance means that we want 
    to return all results matching the given query, and returns 
    it in the "results" argument in the callback function
       */
      db.all('SELECT * FROM temperature', (err, results) => {
        if (err) {
          console.error(err)
        }
        console.log(results)
      })
    })

   /**
     * At this point, we are done with the database. Close the 
    connection after the queries execute
     */
    db.close()

In the preceding code snippet, you learned how to run both read and write queries on our database. Next, let's make a module that specializes in running the database operations for us.