Selecting Specific Fields

Keep on Learning!

If you liked what you've learned so far, dive in!
Subscribe to get access to this tutorial plus
video, code and script downloads.

Start your All-Access Pass
Buy just this tutorial for $6.00

We're on a roll! Let's select more fields - like an average of the numberPrinted and the name of the category, all in one query. Yea yea, we already have the Category's name over here - we're querying for the entire Category object. But just stick with me - it makes for a good example.

Head back to FortuneCookieRepository. As I hope you're guessing, SELECTing more fields is just like SQL: add a comma and get them. You could also use the addSelect() function if you want to get fancy.

Add, AVG(fc.numberPrinted) and give that an alias - fortunesAverage. I'm just making that up. Let's also grab cat.name - the name of the category that we're using here:

... lines 1 - 14
public function countNumberPrintedForCategory(Category $category)
{
return $this->createQueryBuilder('fc')
->andWhere('fc.category = :category')
->setParameter('category', $category)
->select('SUM(fc.numberPrinted) as fortunesPrinted, AVG(fc.numberPrinted) as fortunesAverage, cat.name')
->getQuery()
->getSingleScalarResult();
}
... lines 24 - 26

I don't trust myself. So, var_dump($fortunesPrinted) in the controller with our trusty die statement:

... lines 1 - 35
public function showCategoryAction($id)
{
... lines 38 - 47
$fortunesPrinted = $this->getDoctrine()
->getRepository('AppBundle:FortuneCookie')
->countNumberPrintedForCategory($category);
var_dump($fortunesPrinted);die;
... lines 52 - 56
}
... lines 58 - 59

Refresh! Uh oh, that's an awesome error:

[Semantical Error] line 0, col 88 near 'cat.name FROM': Error 'cat'
is not defined.

Debugging Bad DQL Queries

This is what it looks like when you mess up your DQL. Doctrine does a really good job of lexing and parsing the DQL you give it, so when you make a mistake, it'll give you a pretty detailed error. Here, cat is not defined is because our query references cat with cat.name, but I haven't made any JOINs to create a cat alias. cat is not defined.

But real quick - go back to the error. If you scroll down the stack trace a little, you'll eventually see the full query:

SELECT SUM(fc.numberPrinted) as fortunesPrinted,
    AVG(fc.numberPrinted) fortunesAverage,
    cat.name
    FROM AppBundle\Entity\FortuneCookie fc
    WHERE fc.category = :category

For me, sometimes the top error is so small, it doesn't make sense. But if I look at it in context of the full query, it's a lot easier to figure out what mistake I made.

Fixing our error is easy: we need to add a JOIN - this time an innerJoin(). So, innerJoin('fc.category', 'cat'):

... lines 1 - 14
public function countNumberPrintedForCategory(Category $category)
{
return $this->createQueryBuilder('fc')
... lines 18 - 19
->innerJoin('fc.category', 'cat')
->select('SUM(fc.numberPrinted) as fortunesPrinted, AVG(fc.numberPrinted) as fortunesAverage, cat.name')
... lines 22 - 23
}
... lines 25 - 27

Why fc.category? Because in the FortuneCookie entity, we have a category property. That's how it knows which relationship we're talking about. So cat is now aliased! Let's try again.

Ooook, another error: NonUniqueResultException. We're still finishing the query with getSingleScalarResult(). But now that we're returning multiple columns of data, it doesn't make sense anymore. The NonUniqueResultException means that you either have this situation, or, more commonly, you're using getOneOrNullResult(), but your query is returning mulitple rows. Watch out for that.

Change the query to getOneOrNullResult(): the query still returns only one row, but multiple columns:

... lines 1 - 14
public function countNumberPrintedForCategory(Category $category)
{
return $this->createQueryBuilder('fc')
... lines 18 - 21
->getQuery()
->getOneOrNullResult();
}
... lines 25 - 27

Refresh! Beautiful! The result is an associative array with fortunesPrinted, fortunesAverage and name keys. And notice, we didn't give the category name an alias in the query - we didn't say as something, so it just used name by default:

... lines 1 - 14
public function countNumberPrintedForCategory(Category $category)
{
return $this->createQueryBuilder('fc')
... lines 18 - 20
->select('SUM(fc.numberPrinted) as fortunesPrinted, AVG(fc.numberPrinted) as fortunesAverage, cat.name')
... lines 22 - 23
}
... lines 25 - 27

And hey, I was even a bit messy: for the sum I said as fortunesPrinted but for the average, I just said fortunesAverage with the as. The as is optional - I didn't leave it out on purpose, but hey, good learning moment.

The query is beautiful, so let's actually use our data. In the controller, change the result from $fortunesPrinted to $fortunesData - it's really an array. And below, set $fortunesPrinted to $fortunesData['...']. I'll check my query to remember the alias - it's fortunesPrinted, so I'll use that. I'll do the same thing for the other two fields:

... lines 1 - 35
public function showCategoryAction($id)
{
... lines 38 - 47
$fortunesData = $this->getDoctrine()
->getRepository('AppBundle:FortuneCookie')
->countNumberPrintedForCategory($category);
$fortunesPrinted = $fortunesData['fortunesPrinted'];
$averagePrinted = $fortunesData['fortunesAverage'];
$categoryName = $fortunesData['name'];
... lines 54 - 60
}
... lines 62 - 63

The alias for the average is fortunesAverage. And the last one just uses name. Let's pass these into the template:

... lines 1 - 35
public function showCategoryAction($id)
{
... lines 38 - 54
return $this->render('fortune/showCategory.html.twig',[
'category' => $category,
'fortunesPrinted' => $fortunesPrinted,
'averagePrinted' => $averagePrinted,
'categoryName' => $categoryName
]);
}
... lines 62 - 63

And again, I know, the categoryName is redundant - we already have the whole category object. But to prove things, use categoryName in the template. And below, add an extra line after the total and print averagePrinted:

Moment of truth! Woot! 244,829 total, 81,610 average, and the category name still prints out. Doctrine normally queries for objects, and that's great! But remember, nothing stops you from using that select() function to say: no no no: I don't want to select objects anymore, I want to select specific fields.

Leave a comment!

This course is built on Symfony 2, but most of the concepts apply just fine to newer versions of Symfony. If you have questions, let us know :).

What PHP libraries does this tutorial use?

// composer.json
{
    "require": {
        "php": ">=5.3.3, <7.3.0",
        "symfony/symfony": "2.6.*", // v2.6.13
        "doctrine/orm": "~2.2,>=2.2.3", // v2.4.8
        "doctrine/doctrine-bundle": "~1.2", // 1.6.4
        "twig/extensions": "~1.0", // v1.5.4
        "symfony/assetic-bundle": "~2.3", // v2.8.2
        "symfony/swiftmailer-bundle": "~2.3", // v2.3.12
        "symfony/monolog-bundle": "~2.4", // v2.12.1
        "sensio/distribution-bundle": "~3.0.12", // v3.0.36
        "sensio/framework-extra-bundle": "~3.0", // v3.0.29
        "incenteev/composer-parameter-handler": "~2.0", // v2.1.3
        "hautelook/alice-bundle": "0.2.*" // 0.2
    },
    "require-dev": {
        "sensio/generator-bundle": "~2.3" // v2.5.3
    }
}