How to OrderBy in Many to Many Relationship in Symfony - php

Question

I have two tables products and categories. Products can have many categories and categories can have many products.(The relationship between these two tables is many-to-many)
To map the associations between these two tables I have created another new table product_categories which stores product_id and category_id.
Following is my annotations used in entities to join these three tables.
Product Entity
/**
* #var \Doctrine\Common\Collections\Collection
*
* #ORM\ManyToMany(targetEntity="Category", mappedBy="products")
*/
private $categories;
Category Entity
/**
* #var \Doctrine\Common\Collections\Collection
*
* #ORM\ManyToMany(targetEntity="Product", inversedBy="categories")
* #ORM\JoinTable(name="product_categories",
* joinColumns={
* #ORM\JoinColumn(name="category_id", referencedColumnName="id")
* },
* inverseJoinColumns={
* #ORM\JoinColumn(name="product_id", referencedColumnName="id")
* }
* )
*/
private $products;
Now the problem is, I want to order the records in product_categories into a certain order. So I added a new column called serial_number to product_categories table.
The result what I am trying to achieve is when I am retrieving categories to a product using $product->getCategories() the resulting category array should be ordered by the serial_number.
I have tried the following annotations.
/**
* #var \Doctrine\Common\Collections\Collection
*
* #ORM\ManyToMany(targetEntity="Product", inversedBy="categories")
* #ORM\JoinTable(name="product_categories",
* joinColumns={
* #ORM\JoinColumn(name="category_id", referencedColumnName="id")
* },
* inverseJoinColumns={
* #ORM\JoinColumn(name="product_id", referencedColumnName="id")
* }
* )
* #OrderBy({"product_categories.serial_number"="DESC"})
*/
private $products;
But this results in an annotation syntax error.
Fatal error: Uncaught Doctrine\Common\Annotations\AnnotationException: [Semantical Error] The annotation "#OrderBy" in property ProductBundle\Entity\Product::$products was never imported. Did you maybe forget to add a "use" statement for this annotation? in /var/www/sonicwall.local/app/vendor/doctrine/annotations/lib/Doctrine/Common/Annotations/AnnotationException.php on line 54
When I use #ORM\OrderBy({"product_categories.serial_number"="DESC"}), I do not get a syntax error but results are not getting ordered either.
My question is, is there a way to achieve this using annotations without me having to create new Entities and Repositories for product_categories table?

Answer 1

You have to use #ORM\OrderBy:
#OrderBy acts as an implicit ORDER BY clause for the given fields, that is appended to all the explicitly given ORDER BY items.
All collections of the ordered type are always retrieved in an ordered fashion.
To keep the database impact low, these implicit ORDER BY items are only added to a DQL Query if the collection is fetch joined in the DQL
query.
/**
* #var \Doctrine\Common\Collections\Collection
*
* #ORM\ManyToMany(targetEntity="Product", inversedBy="categories")
* #ORM\JoinTable(name="product_categories",
* joinColumns={
* #ORM\JoinColumn(name="category_id", referencedColumnName="id")
* },
* inverseJoinColumns={
* #ORM\JoinColumn(name="product_id", referencedColumnName="id")
* }
* )
* #ORM\OrderBy({"serialNumber"="DESC"})
*/
private $products;
You tried to do something similar, but with product_categories.serial_number. You do not need product_categories because the order by will try to sort every member of the collection with its own field. So just writing serialNumber will sort by each product serial number.
However, I just saw that you already tried something similar in comments so makes sure to use the attribute name as your field: serialNumber, serial, ... as it appear with $serialNumber