timbrd

Correction, in my case PRIMARY KEY ( reference_ID , ID ) will not work:

ALTER TABLE  <code>wp_9_yarpp_related_cache</code> ADD PRIMARY KEY (  <code>reference_ID</code> ,  <code>ID</code> ) ;
Duplicate entry '43334-28576' for key 'PRIMARY'

I’m using now the following:

CREATE TABLE IF NOT EXISTS wp_9_yarpp_related_cache (
  reference_ID bigint(20) unsigned NOT NULL DEFAULT '0',
  ID bigint(20) unsigned NOT NULL DEFAULT '0',
  score float unsigned NOT NULL DEFAULT '0',
  date timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  KEY reference_ID (reference_ID),
  KEY ID (ID)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;