How to perform complex query building with Doctrine in Symfony?

To perform complex query building with Doctrine in Symfony, you can use Doctrine's QueryBuilder class. Here's a step-by-step guide on how to do this:

Get the EntityManager instance:

First, you need to get the EntityManager instance in your Symfony controller or service. You can do this by injecting the EntityManagerInterface into your constructor, or by using the getDoctrine() method in your controller:

$entityManager = $this->getDoctrine()->getManager();

Create a new QueryBuilder instance:

Next, you need to create a new instance of the QueryBuilder class:

$queryBuilder = $entityManager->createQueryBuilder();

Build your query:

Now, you can start building your query using the various methods provided by the QueryBuilder class. For example, if you want to select data from a specific table, you can use the from() method:

$queryBuilder
    ->select('p')
    ->from('App\Entity\Product', 'p');

You can then add conditions to your query using the where() method:

$queryBuilder
    ->where('p.price > :price')
    ->setParameter('price', 100);

You can also join tables, order results, and group data using the appropriate methods in the QueryBuilder class.

Execute the query:

Finally, you can execute the query and retrieve the results using the getResult() method:

$results = $queryBuilder->getQuery()->getResult();

By following these steps, you can build complex queries using Doctrine's QueryBuilder class in Symfony.