How to create a query in Drupal 8

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, What should I do?

Do I still use `db_select` or `db_query` even though they are deprecated functions? Or create a new controller to extend from "`Select class`" and make my query?

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);

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(" ... ");
}

}

`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();