How to create a query in Drupal 8

Question

I am used to using db_select in drupal 7 but now it\'s deprecated in drupal 8

So, If I need to create a query to list all users from users_field_data table,

Answer 1

As mentioned in the documentation you can query data by injecting Drupal's database connection class. For example:

use Drupal\Core\Database\Connection;

class DatabaseQueryExample {

  protected $connection;

  public function __construct(Connection $connection) {
    $this->connection = $connection;
  }

  public function queryExamples() {
    // db_query()
    $this->connection->query(" ... ");
    // db_select()
    $this->connection->select(" ... ");   
  }

}

Answer 2

db_select, db_insert, db_update, etc... were deprecated in Drupal 8.0.x and will be removed in Drupal 9.0.0.

Instead get a database connection injected into your service from the container and call select() on it. For example, $injected_database->select($table, $alias, $options);.

eg:

$db = \Drupal::database();

$data = $db->select('table_name','t')->fields('t')->execute();

$db->insert();

$db->update();

Answer 3

Depends on what you are trying to achieve.

---

Using the storage object

If you want to make a simple query about the users then you should use the loadByProperties of the storage object

$users = \Drupal::entityTypeManager()->getStorage('user')->loadByProperties([
  'name' => 'bar'
]);

---

Using entity query & loadMultiple

If you need a more complex query with sorts, range, pager and OR/AND condition groups you should use entity query

$ids = \Drupal::entityQuery('user')->condition('name', 'foo')->execute();
$users = User::loadMultiple($ids);