database

\Drupal::database()->merge('rate_karma')
 ->keys(['uid' => $uid])
 ->fields([
   'uid' => $uid,
   'karma' => $results,
 ])
 ->execute();

$connection = Database::getConnection();
$fields = $connection->query("DESCRIBE `my_table`")->fetchAll();
foreach ($fields as $field) {
 if ($field->Field === 'column_name') {
   // Do something.
 }
}

if (\Drupal::database()->schema()->tableExists('my_table')) {
  // Do something.
}

use Drupal\Core\Database\Connection;

/**
 * The database connection.
 */
protected Connection $database;
 
/**
 * Constructs an object.
 *
 * @param \Drupal\Core\Database\Connection $database
 *   The database connection.
 */
public