How can I use the MySQL FIELD function with Doctrine 2\'s ORDER BY clause?

Doctrine 2 MySQL FIELD Function in Order By

When attempting to utilize the SQL FIELD function in the order by clause of a Doctrine 2 query, one may encounter limitations due to its inherent lack of support for this function.

Is There a Doctrine 2 Extension for FIELD?

Fortunately, there exists a Doctrine 2 extension developed by Jeremy Hicks that adds FIELD functionality. To integrate this extension, follow the steps below:

1. Install the extension using Composer:

   composer require doctrine-extensions/doctrine-extensions

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2. Add the extension to the Doctrine configuration:

   <code class="php">$doctrineConfig = $em->getConfiguration();
   $doctrineConfig->addCustomStringFunction('FIELD', 'DoctrineExtensions\Query\Mysql\Field');</code>

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Limitation: FIELD Order By Clause Restrictions

Despite enabling FIELD functionality through the extension, there remains a limitation in Doctrine 2. The FIELD function cannot be used directly in the order by clause.

Solution: Utilizing a HIDDEN Alias

To bypass this restriction, you can employ a HIDDEN field alias in your query:

<code class="php">$qb
    ->select("r, FIELD(r.id, " . implode(", ", $ids) . ") as HIDDEN field")
    ->from("Entities\Round", "r")
    ->where($qb->expr()->in("r.id", $ids))
    ->orderBy("field");</code>

Explanation:

• The HIDDEN keyword prevents the field alias from appearing in the result row.
• By sorting on the HIDDEN field, you effectively sort according to the values returned by the FIELD function.

This workaround allows you to order values within an IN expression in Doctrine 2.2, even with the limitations imposed on the FIELD function in the order by clause.

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