How do you perform left joins in Doctrine ORM when you need to retrieve a user\'s history, including current credits and credit history?

How to Perform Left Joins in Doctrine

This article addresses the issue of executing left joins in Doctrine ORM, a powerful object-relational mapper (ORM) for PHP. The question arises when developers attempt to display a user's current credits alongside their credit history.

Problem Description

The provided code snippet showcases an attempt to create a getHistory function that retrieves the user's history, including their current credits and credit history. However, it encounters a syntax error when using the LEFT JOIN statement.

Solution

To resolve the error, the syntax for performing left joins in Doctrine should be adjusted. There are two main approaches depending on whether an association exists between the entities.

Approach 1: With Associations

If an association is available from UserCreditHistory to User, the following syntax can be used:

<code class="php">public function getHistory($users) {
    $qb = $this->entityManager->createQueryBuilder();
    $qb
        ->select('a', 'u')
        ->from('Credit\Entity\UserCreditHistory', 'a')
        ->leftJoin('a.user', 'u')
        ->where('u = :user')
        ->setParameter('user', $users)
        ->orderBy('a.created_at', 'DESC');

    return $qb->getQuery()->getResult();
}</code>

In this scenario, LEFT JOIN and JOIN produce the same result since a condition is applied to the joined result.

Approach 2: Without Associations

If there is no association from UserCreditHistory to User, the syntax is slightly different:

<code class="php">public function getHistory($users) {
    $qb = $this->entityManager->createQueryBuilder();
    $qb
        ->select('a', 'u')
        ->from('Credit\Entity\UserCreditHistory', 'a')
        ->leftJoin(
            'User\Entity\User',
            'u',
            \Doctrine\ORM\Query\Expr\Join::WITH,
            'a.user = u.id'
        )
        ->where('u = :user')
        ->setParameter('user', $users)
        ->orderBy('a.created_at', 'DESC');

    return $qb->getQuery()->getResult();
}</code>

This will produce a result set that includes both UserCreditHistory and User instances.

The above is the detailed content of How do you perform left joins in Doctrine ORM when you need to retrieve a user\'s history, including current credits and credit history?. For more information, please follow other related articles on the PHP Chinese website!