Symfony2 Select one column in doctrine

问题

I'm trying to refine the query trying to select fewer possible values ​​.. For example I have an entity "Anagrafic" that contains your name, address, city, etc., and a form where I want to change only one of these fields, such as address. I have created this query:

//AnagraficRepository
public function findAddress($Id)
{
     $qb = $this->createQueryBuilder('r')
             ->select('r.address')
             ->where('r.id = :id')
             ->setParameter('id', $Id)
             ->getQuery();

     return $qb->getResult();
}

there is something wrong with this query because I do not return any value, but if I do the query normally:

//Controller
$entity = $em->getRepository('MyBusinessBundle:Anagrafic')->find($id);

Return the right value. How do I do a query selecting only one column?

回答1:

Since you are requesting single column of each record you are bound to expect an array. That being said you should replace getResult with getArrayResult() because you can't enforce object hydration:

$data = $qb->getArrayResult();
Now, you have structure:
    $data[0]['address']
    $data[1]['address']
    ....

Hope this helps.

As for the discussion about performance in comments I generally agree with you for not wanting all 30 column fetch every time. However, in that case, you should consider writing named queries in order to minimize impact if you database ever gets altered.

回答2:

You can use partial objects to only hydrate one field and still return a object.

回答3:

This worked for me:

  $qb = $repository->createQueryBuilder('i')
    ->select('i.name')
    ->...

回答4:

Use partial objects like this to select fields

$qb = $this->createQueryBuilder('r')
    ->select(array('partial r.{id,address}'))
    ...

Put your field names between the brackets

来源：https://stackoverflow.com/questions/15046916/symfony2-select-one-column-in-doctrine