$qb = $this->createQueryBuilder('u');
			$qb->innerJoin('Entities\Client','c')
				//->where('u.client_id = :client_id')
				->where($qb->expr()->like('p.client_id',':client_id'))
				->andWhere('u.username = :username')
				->andWhere('u.password = :password')
				->setParameters(
					array(
						'client_id' => $client_id,
						'username' => $username,
						'password' => $password
					)
			);


$qb->getDql() - outputs:

SELECT u FROM Entities\ClientUser u INNER JOIN Entities\Client c WHERE (p.client_id LIKE :client_id) AND (u.username = :username) AND (u.password = :password)