Sorting with `FIELD()` function in Doctrine

I recently needed to sort query results to match the order of IDs passed to it for use in a WHERE … IN() clause. In MySQL, this can be done using the FIELD() function in the ORDERY BY clause. For Doctrine, which doesn’t have the FIELD() function and doesn’t allow functions in the ORDER BY clause, there’s a little more work needed to make use of it.

In MySQL, sorting to match a given list of IDs can be done like:

SELECT * FROM my_table WHERE id IN(2, 3, 1) ORDER BY FIELD(id, 2, 3, 1);

where id is the field that is both matched and sorted on. The resulting value of the function for a given row is the index position of the second or later argument that matches the first argument, ensuring the results will be returned as ID 2, then 3, then 1.

The first argument to FIELD() is the value used in comparison,

Doctrine doesn’t have the FIELD() function built in, but is extensible to add new functions. The popular Doctrine Extensions repo happens to add this function, among many others. Via composer, that can be added like:

composer require beberlei/doctrineextensions

We already had it installed though, so I commenced trying to get it to work.

I quickly found out that it couldn’t be done in the same way as MySQL, because of Doctrine not allowing functions in the ORDER BY clause. However, it can be added to the SELECT clause and then used by ORDER BY. HIDDEN can be used to prevent it from ending up in the results. This can look like:

$qb =
    ->select('DISTINCT this, FIELD(, :ids) AS HIDDEN orderBySort')
    ->from('MyDB\MyTable', 'this')
    ->where(' IN(:ids)')
    ->orderBy('orderBySort asc')
    ->setParameter('ids', array(2, 3, 1))

This worked perfectly for our needs, and meant I didn’t have to sort them in PHP like I was thinking I might need to.