Left Join in Doctrine: How to Avoid Syntax Errors and Get the Expected Results?

How to Perform a Left Join in Doctrine: Addressing Syntax Errors and Unexpected Results

In Doctrine, a left join allows you to retrieve data from two or more tables while optionally including rows from the left table even if there are no matching rows in the right table. To perform a left join, you can use the leftJoin method.

However, you may encounter some pitfalls while performing left joins. Let's address a common issue and provide a solution.

Issue:
"Syntax Error: Expected DoctrineORMQueryLexer::T_WITH, got 'ON'

Explanation:
In your original code, you used 'ON' instead of 'WITH' in the leftJoin method. The correct syntax for a left join is:

$qb->leftJoin('User\Entity\User', 'u', \Doctrine\ORM\Query\Expr\Join::WITH, 'a.user = u.id')

Updated Code:
Replacing 'ON' with 'WITH' in the above code will resolve the syntax error.

Another Issue:
"Only 1 value from the joined column is being displayed."

Explanation:
If you have an association defined between the tables (CreditEntityUserCreditHistory#user in your example), you can use a simplified version of the left join:

$qb->leftJoin('a.user', 'u')

This will automatically perform a left join based on the association. If no association is defined, you can use the more explicit syntax:

$qb->leftJoin(
    'User\Entity\User',
    'u',
    \Doctrine\ORM\Query\Expr\Join::WITH,
    'a.user = u.id'
)

Result:
The left join will produce a result set that includes rows from both tables, with an optional match from the right table. The result will be returned as an array, where each element is an array of entities:

array(
    array(
        0 => UserCreditHistory instance,
        1 => User instance
    ),
    array(
        0 => UserCreditHistory instance,
        1 => User instance
    ),
    // ...
)

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