🔧 Fixes errors regarding ONLY_FULL_GROUP_BY when using WordPress with managed database services using MySQL 8.

fix.wp-mysql8-onlyfullgroupby.php

<?php

/*
Plugin Name: WP Managed MySQL 8 Fix
Plugin URI: https://gist.github.com/MatheusMK3/4f3acb29ac4fb0e9a03318bcacec1972
Description: Fixes issues regarding MySQL modes (ONLY_FULL_GROUP_BY) when on managed database services.
Author: Matheus Pratta
Version: 1.0.0
Author URI: https://matheus.io
*/

add_action('init', 'wp_fixes_mysql8_full_group_by', -1);
function wp_fixes_mysql8_full_group_by () {
  global $wpdb;

  // Parse all our current modes
  $currentModes = explode(',', array_pop($wpdb->get_results('SELECT @@sql_mode'))->{'@@sql_mode'});

  // Find the offending index (ONLY_FULL_GROUP_BY)
  $removeIndex = array_search('ONLY_FULL_GROUP_BY', $currentModes);

  // If found, unset it
  if (false !== $removeIndex) unset($currentModes[$removeIndex]);

  // Sets the SQL mode
  $wpdb->set_sql_mode($currentModes);
}