Doctrine - 当主键不等于外键时如何获取记录

Question

I'm learning Doctrine by making Symfony application and I have a problem with my code. I'm trying to get all records from flashcards table except for those that are placed inside trash table. In other words I need those flashcards which not exist in trash table.

trash and flashcards are related with one-to-one relation. The flashcards's primary key is the trash's foreign key so I tried something like this:

$qb = $this->createQueryBuilder('f');
$expr = $qb->expr();

$query = $qb
    ->join('f.trash', 't')
    ->andWhere($expr->neq('t.flashcard', 'f.id'))
    ->getQuery()
    ->getResult();

The query is executed properly, there's no errors but also there's no returned records.

Could you write, please, why this ORM code doesn't return any records and could you give me some tips how to make it working?

Thanks in advance for every answer!

Answer 1

What you need is an OUTER JOIN (which you will not find in the Doctrine but keep reading):

Where Table A = flashcards, Table B = trash;

Example Query to get that:

SELECT * FROM TableA
LEFT OUTER JOIN TableB
ON TableA.name = TableB.name
WHERE TableB.id IS null

more read on possible joins and their queries

Using Doctrine does not force you to use its queryBuilder , you can use a plain SQL with Docktrine as well.

All what you need is to build query on your own and execute it with Doctrine connection as in documentation :

use Doctrine\DBAL\DriverManager;

$conn = DriverManager::getConnection($params, $config);

$sql = "SELECT * FROM articles";
$stmt = $conn->query($sql);

There are no RIGHT JOINs, nor OUTER JOINs in Doctrine, my guess is that it is due to the nature of the project which is simplicity and more importantly a portability.

Perhaps this question will also help you somehow if you want to give the query builder the last try.