That works! Thank you!
(I only had to change the first meta_value to meta_key.)
Here’s the final code:
$querystr = "SELECT wposts.*
FROM ".$wpdb->posts." AS wposts
INNER JOIN ".$wpdb->postmeta." AS wpostmeta
ON wpostmeta.post_id = wposts.ID
AND wpostmeta.meta_key = 'event_important'
AND wpostmeta.meta_value = 'on'";
$primary_events = $wpdb->get_results($querystr, OBJECT);
if ($primary_events): ?>
<h1>Events</h1>
<ul>
<?php global $post; ?>
<?php foreach ($primary_events as $post): ?>
<?php setup_postdata($post); ?>
<li><a href="<?php the_permalink() ?>"><?php the_title(); ?><span><?php echo 'Get the Date'; ?></span></a></li>
<?php endforeach; ?>
<?php else : ?>
<h1 class="center">No Events</h1>
<p class="center">Sorry, there are no events yet.</p>
<?php endif; ?>