Wordpress query for multiple post types. Lets say you need to query 3 different post types, and load 1 post from each. Without diving headfirst into SQL and Unions, this is a simpler solution. While may not be the most efficient route, it does the job, and if you can spare less than a second of load/query time, it'll solve your problem.

wp-multiple-post-type-query.php

<?php
  // Add your post types to the array
  $posttypes = array('post_type_1','post_type_3','post_type_3');
  $randompost_typs = shuffle($posttypes);
  $counter = count($posttypes);
  // Add or remove additional post types as needed
  for($i=0; $i<$counter;$i++) {
    if($randompost_typs[$i]=='post_type_1') {
        // I only wanted one post from each, but you can raise or lower the value if needed
        $posts_per_page = 1;
    } elseif($randompost_typs[$i]=='post_type_2') {
        $post_per_page = 1;
    } else {
        $post_per_page = 1;
    }

    // Query arguements
    $args = array(
        'post_type' => $posttypes[$i],
        // Orderby defaults to date, we're just setting it to ensure the latest posts load first
        'orderby'   => 'date
        'posts_per_page' => $post_per_page
    );

  $query = new WP_Query( $args );
  if($query->have_posts()) : while($query->have_posts()): $query->the_post();
    
  // Add your own code for displaying posts below here
?>