Custom Wordpress adjacent post query

wp_adjacent_query.php

<?php 
function get_adjacent_posts_clean($prev = true, $limit = 1, $exclude = '', $date = '') {
  global $wpdb, $post;

  if( empty( $date ) )
    $date = $post->post_date;

  $limit = absint( $limit );
  if( !$limit )
    return;

  $prev_and_next  = $prev ? '<' : '>';
  $exclude_string = (!empty($exclude)) ? 'AND tt1.term_id NOT IN(' . $exclude . ')' : ''; // put fallback in for array

  $p = $wpdb->get_results( "
  (
    SELECT p.post_date, p.post_title
    FROM $wpdb->posts AS p 
    INNER JOIN $wpdb->term_relationships AS tr ON p.ID = tr.object_id
    INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
    WHERE 
      p.post_date " . $prev_and_next . " '$date'
      AND p.post_type = 'post'
      AND p.post_status = 'publish'
      AND tt.taxonomy = 'category'
      " . $exclude_string . "
    ORDER by 
      p.post_date DESC
    LIMIT 
      $limit
  )
  ORDER by post_date ASC ");  
  return $p;
}
?>

This isn't really meant to be used as is, there's some spots where this query would break. Just a good starting point if wanting to write a more custom adjacent post query than what is provided by WP core.

Original query modified from here