Regarding term clarification in the database api

Question

So I was making a custom block, and implemented the build() method.

public function build() {
    $result = $connection->db_query("SELECT n.title, u.uid, n.created    FROM node_field_data n, users u WHERE u.uid = n.uid AND n.type = :type ORDER BY n.created DESC LIMIT 5", array(
        'type' => 'article',
    ));
    $content = '';
    if ($result) {
        while ($row = $result->fetchAssoc()) {
            $content .= '<li>' . $row['title'] . '</li>';
        }
    } else {
        $content .= 'No blog posts to show';
    }

    return array(
        '#markup' => '<ul>' . $content . '</ul>',
    );
}

So this is a pretty basic helloworld kind of example calling the database. But db_query is deprecated with the following surgestion:

     * @deprecated as of Drupal 8.0.x, will be removed in Drupal 9.0.0. Instead, get
     *   a database connection injected into your service from the container and
     *   call query() on it. E.g.
     *   $injected_database->query($query, $args, $options);

The surgestion seemed kind of spacey not entirely knowing all of the expressions but i eventually fixed it with the following code:

    $connection = \Drupal::database();
    $result = $connection->query("SELECT n.title, u.uid, n.created FROM node_field_data n, users u WHERE u.uid = n.uid AND n.type = :type ORDER BY n.created DESC LIMIT 5", array(
        'type' => 'article',
    ));

to call the database.

My question is, \Drupal::database() is a static method, and i call it from inside of my own block, am i doing it wrong? or am i misunderstanding their meaning of dependency injection? if i had to do DI in other web programming i would find the DI container and configure it to give the database into my constructor or via a accessor method right?

Follow up questions is

1. What exactly constitutes my container?

2. What is "my service" referring to? my module maybe?

Answer 1

Yes, you are doing it wrong by calling \Drupal::database.

Look at Drupal\block_content\Plugin\Block\BlockContentBlock in core as an example. The create() method gets the services and passes them to the __construct() method. That is the proper way.