Symfony2 and Doctrine - Error: Invalid PathExpression. Must be a StateFieldPathExpression

问题

I have an entity that looks like this:

/**
 * @Gedmo\\Tree(type=\"nested\")
 * @ORM\\Table(name=\"categories\")
 * @ORM\\Entity()
 */
class Category extends BaseCategory
{

    /**
    * @ORM\\OneToMany(targetEntity=\"Category\", mappedBy=\"parent\")
    */
    protected $children;

    /**
    * @Gedmo\\TreeParent
    * @ORM\\ManyToOne(targetEntity=\"Category\", inversedBy=\"children\")
    * @ORM\\JoinColumn(name=\"parent_id\", referencedColumnName=\"id\", onDelete=\"SET NULL\")
    */
    protected $parent;

}

and I am trying to run a query like this:

$qb = $this->em->createQueryBuilder()
            ->select(\'c.parent\')
            ->from(\'Category\', \'c\');

$result = $qb->getQuery()->getArrayResult();

However, I am getting the following error:

[Semantical Error] ... Error: Invalid PathExpression. Must be a StateFieldPathExpression.

How can I select the parent_id field from my table. I have tried a bunch of variations and even if I do something like this:

$qb = $this->em->createQueryBuilder()
            ->select(\'c\')
            ->from(\'Category\', \'c\');

I get all fields in the table except for the parent_id. This seems like Doctrine is getting in the way. How can I query for this parent_id field? or better yet how can I get all fields in the table including the parent_id

回答1:

You can use the currently undocumented IDENTITY function to select the FK IDs in a query:

SELECT IDENTITY(c.parent) ...

回答2:

Solution using createQueryBuilder:

$query->SELECT('pa.id')
        ->from('Category', 'ca');
$query->join('ca.parent', 'pa');

$result = $query->getQuery()->getArrayResult();

回答3:

You are selecting an object that is not joined. Like said in another answer, you have to do something like :

qb->innerJoin("c.parent", "p")

来源：https://stackoverflow.com/questions/14216470/symfony2-and-doctrine-error-invalid-pathexpression-must-be-a-statefieldpathe

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symfony

doctrine-orm

dql