Drupal 8 Install Table and Add Field

Drupal 8 Install Table and Add Field

<?php
use Drupal\Core\Database\Database;
/**
 * Implements hook_schema().
 */
function dots_schema() {
  $schema['dots_table'] = [
  'description' => 'dots table',
    'fields' => [
      'id' => [
        'type' => 'serial',
        'unsigned' => TRUE,
        'not null' => TRUE,
        'description' => "dots id.",
      ],
      'name' => [
        'description' => 'dots name.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
      'email' => [
        'description' => 'dots email.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
      'mobile' => [
        'description' => 'dots mobile.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
      'dob' => [
        'description' => 'dots dob.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
      'gender' => [
        'description' => 'dots gender.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
      'created' => [
        'description' => 'dots created.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
      'changed' => [
        'description' => 'dots changed.',
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],
/*      'node_id' => [
        'description' => 'dots node id',
        'type' => 'int',
        'length' => 255,
        'not null' => TRUE,
        'default' => ''
      ],*/
    ],
    'primary key' => ['id'],
  ];

  return $schema;
}

function dots_update_8002() {
  $spec = array(
    'type' => 'int',
    'description' => "dots node id",
    'length' => 20,
  ); 
  $schema = Database::getConnection()->schema();
  $schema->addField('dots_table', 'node_id', $spec);
}

function dots_update_8003() {
  $spec = array(
    'type' => 'int',
    'description' => "dots user uid",
    'length' => 20,
  ); 
  $schema = Database::getConnection()->schema();
  $schema->addField('dots_table', 'user_id', $spec);
}