NodeJS mysql query returns empty result

Question

i'm new to NodeJS (duh!). I know it executes functions asynchronous but I still cannot see what causes this phenomenon:

I am using the express and mysql modules and trying to execute an SQL query based on request parameters. It is supposed to be a simple validation API feature where the server is going to lookup a user in a database by listening on a specific URL for two request parameters (user and passwd).

The problem is that the SQL query always returns an empty object as result when I do this using the request parameters in the query.

However, if i hard code the query and run it outside the app.get(...) I get the desired result! But I need this to work on demand by request...

(I'm not intending to use GET-request later on, this example is for debugging purposes :))

What am i doing wrong here?

Here's my code:

// Server and Mysql setup here 
var app = require('express').createServer(),
    SERVER_PORT = 8080;
var Client = require('mysql').Client,
    client = new Client(),
    ...
// User, password and database setup here, cropped out from this example //
// ...

function validateUser(user, passwd, callback) {
client.query('SELECT date FROM '+CUSTOMERS_TABLE+' WHERE email="'+user+'" AND passwd="'+passwd+'";',
    function selectCb(err, results, fields) {
        if (err) {
            throw err;
        }
        console.log(fields);
        callback(results);
    });
}

app.get('/', function(req, res){
var url_parts = url.parse(req.url, true);
var query = url_parts.query;
if((typeof query[REQ_PARAM_USER] != 'undefined' && typeof query[REQ_PARAM_PASSWD] != 'undefined')
        && (query[REQ_PARAM_USER] != '' && query[REQ_PARAM_PASSWD] != '')) {
        validateUser(REQ_PARAM_USER, REQ_PARAM_PASSWD, function(results) {
            console.log(results);
        });
    }
    res.end("End")
});
app.listen(SERVER_PORT);

console.log('Server running at port '+SERVER_PORT);

Oh, and by the way, console.log(fields) outputs the correct fields! But why not the results?

Linus Thiel · Accepted Answer · 2012-03-28 11:04:22Z

You are passing the wrong parameters to validateUser:

validateUser(REQ_PARAM_USER, REQ_PARAM_PASSWD, // ...

What you really want:

validateUser(query[REQ_PARAM_USER], query[REQ_PARAM_PASSWD], // ...

Edit: A few other issues with your code:

You don't have to parse the url. Express does this for you, and the query is available as req.query.
You shouldn't throw in asynchronous code. It will give unexpected results. Instead, stick to the nodejs paradigm of passing (err, results) to all callbacks, and do proper error checking where you can -- i.e., in your verifyUser, pass along the error with the callback and check for errors in your get handler. Either res.send(500) (or something) when you get an error, or pass it along to the express error handler by calling next(err).
```
validateUser(query[REQ_PARAM_USER], query[REQ_PARAM_PASSWD], function(err, results) {
    if(err) {
        console.error(err);
        res.send(500);
    } else {
        console.log(results);
        res.send(results);
    }
});
```
Never pass query parameters directly to something like an SQL query. Instead, use parameters for your SQL query:
```
client.query('SELECT date FROM '+CUSTOMERS_TABLE+' WHERE email=? AND passwd=?', [user, passwd], // ...
```

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