Trying to join two simple tables using Doctrine 2

Question

I'm quite a beginner at Symfony 2 and Doctrine 2. I have two models a Blog post and Comment . They are related to each other by blog_id FK inside comment table.

I just want to create a simple method that takes a blog id, Retrieves that blog and related comments. Instead of doing another query in lazy-loading the related comments.

Here's what i tried :

<?php

namespace Blogger\BlogBundle\Entity\Repository;

use Doctrine\ORM\EntityRepository;

class BlogRepository extends EntityRepository
{

    public function getBlogWithComments($id)
    {
        $query = $this->getEntityManager()->createQuery('
                    SELECT b, c
                    FROM BloggerBlogBundle:Blog b
                    WHERE b.id = :id
                    JOIN b.id c
                    WHERE b.id = c.blog');
        $query->setParameter("id", $id);
        return $query->getResult();

    }
}

I'm really a beginner at Doctrine 2. I usually use Query Builder, But i have no idea how to make a join using it. So Tried it in DQL, Couldn't figure it out either.

It gives me this syntax error whenever i try to call getBlogWithComments method:

[Syntax Error] line 0, col 80: Error: Expected end of string, got 'JOIN'

All what i want to know is that, How to write JOIN statements using Query Builder and DQL ? Knowing that documentation is not that helpful unfortunately.

Answer 1

A JOIN with DQL is done by referencing the relationship between the entities and it only needs to go one way. What I mean is b.comment c is all that is needed, there is no need for referencing c.blog .

public function getBlogWithComments($id)
{
    return $this->getEntityManager()
           ->createQuery('
                SELECT b, c
                FROM BloggerBlogBundle:Blog b
                JOIN b.comment c
                WHERE b.id = :id
            ')
            ->setParameter("id", $id)
            ->getResult();

}