Multiple Autocomplete search for form text field?

Question

Drupal

Guys, I'm dumb. Tell me, in general, there is a form with a text field, to which autocomplete is attached, the callback itself looks like this:

<?php

function searchform_autocomplete_search($string) {
  
  $matches = array();
  
  $result = db_select('field_data_field_sku', 't')
    ->fields('t', array('field_sku_value'))
    ->condition('field_sku_value', '%' . db_like($string) . '%', 'LIKE')
    ->range(0, 10)
    ->execute()
    ->fetchAll();
  
  foreach ($result as $row) {
    $matches[$row->field_sku_value] = check_plain($row->field_sku_value);
  }

  drupal_json_output($matches);
  
}

in fact, everything is simple if the search goes through one table. I need to fasten the search on 2 tables to this, the name for the example of the 2nd table is field_data_field_new_sku. Besides, what to concoct the 2nd query on the second table, nothing comes to mind. I think there is a beautiful option, how to pull values ​​from 2 tables in one query to the database?