Got this one myself, so it’s solved now – it’s due to a problem/error in MySQL v. 5.0.51 that creates this behaviour. Upgrading to 5.0.52 resolves this. If that’s not possible, I found this piece of code that can be used instead as plugin…
<?php
/*
Plugin Name: 123 No Group By ID
Plugin URI:
Description: Changes the GROUP BY id in GROUP BY post_date (Problem from MySQL 5.0.51).
Author: Ingo Henze
Version: 0.10
Author URI: http://putzlowitsch.de/
*/
// GROUP BY auswerten
function plw123ngb_posts_groupby( $groupby ) {
if( preg_match( “/(|[ ,.])id(|[ ,])/i”, $groupby ) )
$groupby = ‘post_date’;
return $groupby;
}
add_filter( ‘posts_groupby’, ‘plw123ngb_posts_groupby’ );
?>
