function userInvestments() {
// Make the Wordpress database a global:
global $wpdb;
global $current_user;

// Get the current user:
get_currentuserinfo();
$userID = $current_user->ID;

if( !empty($userID) )
{
    // Run the query to get the Post IDs:
    $results = $wpdb->get_results("SELECT DISTINCT(post_id) FROM wp_postmeta WHERE meta_key = 'investors_attach' AND meta_value LIKE '%\"1\"%'" );

    // $results now contains an array as follows:No
    // [
    //    { post_id: 1 },
    //    { post_id: 2 },
    //    ...
    //    { post_id: 19 },
    // ]

    // You will need to output the results as follows:
    foreach( $results as $p )
    {
        echo $p['post_id'];
    }
}
}

/* add new tab called "mytab" */

add_filter('um_account_page_default_tabs_hook', 'my_portfolio_tab_in_um', 100 );
function my_portfolio_tab_in_um( $tabs ) {
  $tabs[800]['myportfolio']['icon'] = 'um-faicon-pencil';
  $tabs[800]['myportfolio']['title'] = 'My Portfolio';
  $tabs[800]['myportfolio']['custom'] = true;
  return $tabs;
}

/* make our new tab hookable */

add_action('um_account_tab__myportfolio', 'um_account_tab__myportfolio');
function um_account_tab__myportfolio( $info ) {
  global $ultimatemember;
  extract( $info );

  $output = $ultimatemember->account->get_tab_output('myportfolio');
  if ( $output ) { echo $output; }
}

/* Finally we add some content in the tab */

add_filter('um_account_content_hook_myportfolio', 'um_account_content_hook_myportfolio');
function um_account_content_hook_myportfolio( $output ){
  ob_start();
  ?>

  <div class="um-field">
    <h2>My Portfolio</h2> Debug
    <?php userInvestments(); ?>
  </div>

  <?php

  $output .= ob_get_contents();
  ob_end_clean();
  return $output;
}