# Problem with Database querying in NodeJS **URL:** \ **Category:** General\ **Created:** [September 2, 2017, 4:52pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399 "2017-09-02T16:52:41Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![hamza-hajji](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/hamza-hajji/32/70730_2.png) [@hamza-hajji](https://forum.freecodecamp.org/u/hamza-hajji)\ **Post date:** [September 2, 2017, 4:52pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/1 "2017-09-02T16:52:41Z")
I’m working on the URL Shortener API, I store the data in the database and when i try to retrieve it with a get route, this happens: this is the code ```javascript app.route('/:short_url_index') .get(function (req, res) { MongoClient.connect(Mongo_URI, function (err, db) { if (err) return console.log('Error connecting to the Database', err); var short_url_index = parseInt(req.params.short_url_index); db.collection('urls').findOne({ short_url_index: short_url_index }, function (err, doc) { res.redirect(doc.original_url); }); db.close(); }); }); ``` i’m basically trying to query the database by the short url and get the original url, but i get this error in the cmd: ```auto Node.js listening ... * * C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb\lib\utils.js:123 process.nextTick(function() { throw err; }); ^ TypeError: Cannot read property 'original_url' of null at C:\Users\hamza\Desktop\url_shortener\server.js:100:25 at handleCallback (C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb\lib\utils.js:120:56) at C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb\lib\collection.js:1417:5 at handleCallback (C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb\lib\utils.js:120:56) at C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb\lib\cursor.js:682:5 at handleCallback (C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb-core\lib\cursor.js:171:5) at setCursorNotified (C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb-core\lib\cursor.js:515:3) at C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb-core\lib\cursor.js:590:16 at queryCallback (C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb-core\lib\cursor.js:232:18) at C:\Users\hamza\Desktop\url_shortener\node_modules\mongodb-core\lib\connection\pool.js:469:18 [nodemon] app crashed - waiting for file changes before starting... ``` but when i try to log the document retrieved from the database, i get it correctly and it’s not undefined ---
**Author:** ![ppc](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/ppc/32/63349_2.png) [@ppc](https://forum.freecodecamp.org/u/ppc)\ **Post date:** [September 2, 2017, 5:33pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/2 "2017-09-02T17:33:38Z")
findOne callback needs to check the error parameter - it will show the problem ---
**Author:** ![hamza-hajji](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/hamza-hajji/32/70730_2.png) [@hamza-hajji](https://forum.freecodecamp.org/u/hamza-hajji)\ **Post date:** [September 2, 2017, 5:43pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/3 "2017-09-02T17:43:03Z")
Added the error check, and i’m still having the same problem ```javascript if (err) res.status(400).send({error: err}); ``` ---
**Author:** ![ppc](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/ppc/32/63349_2.png) [@ppc](https://forum.freecodecamp.org/u/ppc)\ **Post date:** [September 2, 2017, 5:47pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/4 "2017-09-02T17:47:38Z")
what does the error say? since there is an error you cannot use the `doc` parameter ---
**Author:** ![hamza-hajji](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/hamza-hajji/32/70730_2.png) [@hamza-hajji](https://forum.freecodecamp.org/u/hamza-hajji)\ **Post date:** [September 2, 2017, 5:49pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/5 "2017-09-02T17:49:26Z")
It just throws the same error: and i don’t see any response in postman ---
**Author:** ![ppc](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/ppc/32/63349_2.png) [@ppc](https://forum.freecodecamp.org/u/ppc)\ **Post date:** [September 2, 2017, 5:55pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/7 "2017-09-02T17:55:42Z")
the problem is db.close() is called right after findOne which is async ---
**Author:** ![hamza-hajji](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/hamza-hajji/32/70730_2.png) [@hamza-hajji](https://forum.freecodecamp.org/u/hamza-hajji)\ **Post date:** [September 2, 2017, 5:56pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/8 "2017-09-02T17:56:57Z")
what’s the solution to this? should i use promises? ---
**Author:** ![hamza-hajji](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/hamza-hajji/32/70730_2.png) [@hamza-hajji](https://forum.freecodecamp.org/u/hamza-hajji)\ **Post date:** [September 2, 2017, 6:02pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/9 "2017-09-02T18:02:29Z")
Here’s what i did: ```auto db.collection('urls').findOne({ short_url_index: short_url_index }).then(function (doc) { res.redirect(doc.original_url); console.log(doc); }).catch(function (err) { res.send({error: err}); }); db.close(); ``` and this is the response ```auto { _id: 59aadc0b918df030bcc216d7, original_url: 'www.google.com', short_url_index: 3432, short_url: 'http://localhost:3000/3432' } ``` this makes it way more confusing, if i can get the object back, why can’t i get its property? ---
**Author:** ![ppc](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/ppc/32/63349_2.png) [@ppc](https://forum.freecodecamp.org/u/ppc)\ **Post date:** [September 2, 2017, 6:03pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/10 "2017-09-02T18:03:41Z")
you cannot close the db until the work is done - the work is done in the `findOne` callback - so close must be called in the callback promises make async code look cleaner - arguably they make async solutions easier but you must understand promises first - and the best use of promises now is with async/await supported in node ---
**Author:** ![ppc](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/ppc/32/63349_2.png) [@ppc](https://forum.freecodecamp.org/u/ppc)\ **Post date:** [September 2, 2017, 6:16pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/11 "2017-09-02T18:16:01Z")
your promises version has the same async logic problem aka race condition - a little easier to fix with promises - put `db.close()` in a final then in the future there may be a promises `finally` ---
**Author:** ![hamza-hajji](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/hamza-hajji/32/70730_2.png) [@hamza-hajji](https://forum.freecodecamp.org/u/hamza-hajji)\ **Post date:** [September 2, 2017, 6:21pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/12 "2017-09-02T18:21:07Z")
Even if i put the db.close() call into the callback, it does the same thing. I don’t think how i handle the async is important because event if i comment out the close call it does the same thing. and this is the response i get from the catch() call ```auto { "error": {} } ``` ---
**Author:** ![ILM](https://sea3.discourse-cdn.com/freecodecamp/user_avatar/forum.freecodecamp.org/ilm/32/363239_2.png) [@ILM](https://forum.freecodecamp.org/u/ILM)\ **Post date:** [January 16, 2021, 5:59pm UTC](https://forum.freecodecamp.org/t/problem-with-database-querying-in-nodejs/145399/13 "2021-01-16T17:59:37Z")
Closed on January 16, 2021, 5:59pm UTC