I have the key, in Sqylog as:
Indexes: PRIMARY
Columns: realmid,accid
Unique: Checked
Also, here is the create script from the current realmd.sql:
--
-- Table structure for table `realmcharacters`
--
DROP TABLE IF EXISTS `realmcharacters`;
CREATE TABLE `realmcharacters` (
`realmid` int(11) unsigned NOT NULL default '0',
`acctid` bigint(20) unsigned NOT NULL,
`numchars` tinyint(3) unsigned NOT NULL default '0',
PRIMARY KEY (`realmid`,`acctid`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC COMMENT='Realm Character Tracker';
However, doing this join will still lead to a table scan and not using an index, hence the need for an index.