Symfony2 Doctrine get random product from a category

Question

I have the following database scheme:

table \'products\'
id
category_id

and of course a category table, just with an id.

The data look

Answer 1

You first have to count the total number of products, then generate a random offset to select a random product.

This should get you started:

$count = $this->createQueryBuilder('u')
             ->select('COUNT(u)')
             ->getQuery()
             ->getSingleScalarResult();

And then you can generate a random number between your 1 and the total number of rows.

return $this->createQueryBuilder('u')
    ->where('u.category = :category')
    ->setFirstResult(rand(0, $count - 1))
    ->setMaxResults(1)
    ->setParameter('category', $category->getId())
    ->getQuery()
    ->getSingleResult()
;

Which translates to:

SELECT * FROM products WHERE category_id = ? LIMIT 1, {random offset}